Plants and seeds of corn variety I363128

ABSTRACT

According to the invention, there is provided seed and plants of the corn variety designated I363128. This invention thus relates to the plants, seeds and tissue cultures of the variety I363128, and to methods for producing a corn plant produced by crossing a corn plant of variety I363128 with itself or with another corn plant, such as a plant of another variety. This invention further relates to corn seeds and plants produced by crossing plants of variety I363128 with plants of another variety, such as another inbred line, and to crosses with related species. This invention further relates to the inbred and hybrid genetic complements of plants of variety I363128, and also to the SSR and isozyme typing profiles of corn variety I363128.

This application claims the priority of U.S. Provisional PatentApplication Ser. No. 60/269,755, filed Feb. 16, 2001, the entiredisclosure of which is specifically incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of corn breeding.In particular, the invention relates to inbred corn seed and plants ofthe variety designated I363128, and derivatives and tissue culturesthereof.

2. Description of Related Art

The goal of field crop breeding is to combine various desirable traitsin a single variety/hybrid. Such desirable traits include greater yield,better stalks, better roots, resistance to insecticides, herbicides,pests, and disease, tolerance to heat and drought, reduced time to cropmaturity, better agronomic quality, higher nutritional value, anduniformity in germination times, stand establishment, growth rate,maturity, and fruit size.

Breeding techniques take advantage of a plant's method of pollination.There are two general methods of pollination: a plant self-pollinates ifpollen from one flower is transferred to the same or another flower ofthe same plant. A plant cross-pollinates if pollen comes to it from aflower on a different plant.

Corn plants (Zea mays L.) can be bred by both self-pollination andcross-pollination. Both types of pollination involve the corn plant'sflowers. Corn has separate male and female flowers on the same plant,located on the tassel and the ear, respectively. Natural pollinationoccurs in corn when wind blows pollen from the tassels to the silks thatprotrude from the tops of the ear shoot.

Plants that have been self-pollinated and selected for type over manygenerations become homozygous at almost all gene loci and produce auniform population of true breeding progeny, a homozygous plant. A crossbetween two such homozygous plants produces a uniform population ofhybrid plants that are heterozygous for many gene loci. Conversely, across of two plants each heterozygous at a number of loci produces apopulation of hybrid plants that differ genetically and are not uniform.The resulting non-uniformity makes performance unpredictable.

The development of uniform corn plant hybrids requires the developmentof homozygous inbred plants, the crossing of these inbred plants, andthe evaluation of the crosses. Pedigree breeding and recurrent selectionare examples of breeding methods used to develop inbred plants frombreeding populations. Those breeding methods combine the geneticbackgrounds from two or more inbred plants or various other broad-basedsources into breeding pools from which new inbred plants are developedby selfing and selection of desired phenotypes. The new inbreds arecrossed with other inbred plants and the hybrids from these crosses areevaluated to determine which of those have commercial potential.

The pedigree breeding method involves crossing two genotypes. Eachgenotype can have one or more desirable characteristics lacking in theother, or, each genotype can complement the other. If the two originalparental genotypes do not provide all of the desired characteristics,other genotypes can be included in the breeding population. Superiorplants that are the products of these crosses are selfed and selected insuccessive generations. Each succeeding generation becomes morehomogeneous as a result of self-pollination and selection. Typically,this method of breeding involves five or more generations of selfing andselection: S₁→S₂; S₂→S₃; S₃→S₄; S₄→S₅, etc. After at least fivegenerations, the inbred plant is considered genetically pure.

Backcrossing can also be used to improve an inbred plant. Backcrossingtransfers a specific desirable trait from one inbred or non-inbredsource to an inbred that lacks that trait. This can be accomplished, forexample, by first crossing a superior inbred (A) (recurrent parent) to adonor inbred (non-recurrent parent), which carries the appropriate locusor loci for the trait in question. The progeny of this cross are thenmated back to the superior recurrent parent (A) followed by selection inthe resultant progeny for the desired trait to be transferred from thenon-recurrent parent. After five or more backcross generations withselection for the desired trait, the progeny are heterozygous for locicontrolling the characteristic being transferred, but are like thesuperior parent for most or almost all other loci. The last backcrossgeneration would be selfed to give pure breeding progeny for the traitbeing transferred.

A single cross hybrid corn variety is the cross of two inbred plants,each of which has a genotype which complements the genotype of theother. The hybrid progeny of the first generation is designated F₁.Typically, F₁ hybrids are more vigorous than their inbred parents. Thishybrid vigor, or heterosis, is manifested in many polygenic traits,including markedly improved yields, better stalks, better roots, betteruniformity and better insect and disease resistance. In the developmentof hybrids only the F₁ hybrid plants are typically sought. An F₁ singlecross hybrid is produced when two inbred plants are crossed. A doublecross hybrid is produced from four inbred plants crossed in pairs (A×Band C×D) and then the two F₁ hybrids are crossed again (A×B)×(C×D).

The development of a hybrid corn variety involves three steps: (1) theselection of plants from various germplasm pools; (2) the selfing of theselected plants for several generations to produce a series of inbredplants, which, although different from each other, each breed true andare highly uniform; and (3) crossing the selected inbred plants withunrelated inbred plants to produce the hybrid progeny (F₁). During theinbreeding process in corn, the vigor of the plants decreases. Vigor isrestored when two unrelated inbred plants are crossed to produce thehybrid progeny (F₁). An important consequence of the homozygosity andhomogeneity of the inbred plants is that the hybrid between any twoinbreds is always the same. Once the inbreds that give a superior hybridhave been identified, hybrid seed can be reproduced indefinitely as longas the homogeneity of the inbred parents is maintained. Conversely, muchof the hybrid vigor exhibited by F₁ hybrids is lost in the nextgeneration F₂). Consequently, seed from hybrid varieties is not used forplanting stock. It is not generally beneficial for farmers to save seedof F₁ hybrids. Rather, farmers purchase F₁ hybrid seed for plantingevery year.

North American farmers plant tens of millions of acres of corn at thepresent time and there are extensive national and internationalcommercial corn breeding programs. A continuing goal of these cornbreeding programs is to develop corn hybrids that are based on stableinbred plants and have one or more desirable characteristics. Toaccomplish this goal, the corn breeder must select and develop superiorinbred parental plants.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a corn plant of thevariety designated I363128. Also provided are corn plants having all thephysiological and morphological characteristics of the inbred cornvariety I363128. The inbred corn plant of the invention may furthercomprise, or have, a cytoplasmic or nuclear factor that is capable ofconferring male sterility or otherwise preventing self-pollination, suchas by self-incompatibility. Parts of the corn plant of the presentinvention are also provided, for example, pollen obtained from an inbredplant and an ovule of the inbred plant.

The invention also concerns seed of the inbred corn variety I363128. Asample of this seed has been deposited under ATCC Accession No.PTA-4494. The inbred corn seed of the invention may be provided as anessentially homogeneous population of inbred corn seed of the varietydesignated I363128. Essentially homogeneous populations of inbred seedare those that consist essentially of the particular inbred seed, andare generally free from substantial numbers of other seed, so that theinbred seed forms between about 90% and about 100% of the total seed,and preferably, between about 95% and about 100% of the total seed. Mostpreferably, an essentially homogeneous population of inbred corn seedwill contain between about 98.5%, 99%, 99.5% and about 99.9% of inbredseed, as measured by seed grow outs. This corresponds to currentcommercial practice among the leading companies in the seed industry.

Therefore, in the practice of the present invention, inbred seedgenerally forms at least about 97% of the total seed. However, even if apopulation of inbred corn seed was found, for some reason, to containabout 50%, or even about 20/% or 15% of inbred seed, this would still bedistinguished from the small fraction (generally less than 2% andpreferably less than 1%) of inbred seed that may be found within apopulation of hybrid seed, e.g., within a commercial bag of hybrid seed.In such a bag of hybrid seed offered for sale, Federal regulationsrequire that the hybrid seed be at least about 95% of the total seed, orbe labeled as a mixture. In the most preferred practice of theinvention, the female inbred seed that may be found within a bag ofhybrid seed will be about 1% of the total seed, or less, and the maleinbred seed that may be found within a bag of hybrid seed will benegligible, i.e., will be on the order of about a maximum of 1 per100,000, and usually less than this value.

The population of inbred corn seed of the invention can further beparticularly defined as being essentially free from hybrid seed. Theinbred seed population may be separately grown to provide an essentiallyhomogeneous population of inbred corn plants designated I363128.

In another aspect of the invention, single locus converted plants ofvariety I363128 are provided. The single transferred locus maypreferably be a dominant or recessive allele. Preferably, the singletransferred locus will confer such traits as male sterility, yieldstability, waxy starch, yield enhancement, industrial usage, herbicideresistance, insect resistance, resistance to bacterial, fungal nematodeor viral disease, male fertility, and enhanced nutritional quality. Thesingle locus may be a naturally occurring maize gene introduced into thegenome of the variety by backcrossing, a natural or induced mutation, ora transgene introduced through genetic transformation techniques. Whenintroduced through transformation, a single locus may comprise one ormore transgenes integrated at a single chromosomal location.

In yet another aspect of the invention, an inbred corn plant of thevariety designated I363128 is provided, wherein acytoplasmically-inherited trait has been introduced into said inbredplant. Such cytoplasmically-inherited traits are passed to progenythrough the female parent in a particular cross. An exemplarycytoplasmically-inherited trait is the male sterility trait.Cytoplasmic-male sterility (CMS) is a pollen abortion phenomenondetermined by the interaction between the genes in the cytoplasm and thenucleus. Alteration in the mitochondrial genome and the lack of restorergenes in the nucleus will lead to pollen abortion. With either a normalcytoplasm or the presence of restorer gene(s) in the nucleus, the plantwill produce pollen normally. A CMS plant can be pollinated by amaintainer version of the same variety, which has a normal cytoplasm butlacks the restorer gene(s) in the nucleus, and continue to be malesterile in the next generation. The male fertility of a CMS plant can berestored by a restorer version of the same variety, which must have therestorer gene(s) in the nucleus. With the restorer gene(s) in thenucleus, the offspring of the male-sterile plant can produce normalpollen grains and propagate. A cytoplasmically inherited trait may be anaturally occurring maize trait or a trait introduced through genetictransformation techniques.

In another aspect of the invention, a tissue culture of regenerablecells of a plant of variety I363128 is provided. The tissue culture willpreferably be capable of regenerating plants capable of expressing allof the physiological and morphological characteristics of the variety,and of regenerating plants having substantially the same genotype asother plants of the variety. Examples of some of the physiological andmorphological characteristics of the variety I363128 includecharacteristics related to yield, maturity, and kernel quality, each ofwhich is specifically disclosed herein. The regenerable cells in suchtissue cultures will preferably be derived from embryos, meristematiccells, immature tassels, microspores, pollen, leaves, anthers, roots,root tips, silk, flowers, kernels, ears, cobs, husks, or stalks, or fromcallus or protoplasts derived from those tissues. Still further, thepresent invention provides corn plants regenerated from the tissuecultures of the invention, the plants having all the physiological andmorphological characteristics of variety I363128.

In yet another aspect of the invention, processes are provided forproducing corn seeds or plants, which processes generally comprisecrossing a first parent corn plant with a second parent corn plant,wherein at least one of the first or second parent corn plants is aplant of the variety designated I363128. These processes may be furtherexemplified as processes for preparing hybrid corn seed or plants,wherein a first inbred corn plant is crossed with a second corn plant ofa different, distinct variety to provide a hybrid that has, as one ofits parents, the inbred corn plant variety I363128. In these processes,crossing will result in the production of seed. The seed productionoccurs regardless of whether the seed is collected or not.

In a preferred embodiment of the invention, the first step in “crossing”comprises planting, preferably in pollinating proximity, seeds of afirst and second parent corn plant, and preferably, seeds of a firstinbred corn plant and a second, distinct inbred corn plant. Where theplants are not in pollinating proximity, pollination can nevertheless beaccomplished by transferring a pollen or tassel bag from one plant tothe other as described below.

A second step comprises cultivating or growing the seeds of said firstand second parent corn plants into plants that bear flowers. Corn bearsboth male flowers (tassels) and female flowers (silks) in separateanatomical structures on the same plant.

A third step comprises preventing self-pollination of the plants, i.e.,preventing the silks of a plant from being fertilized by any plant ofthe same variety, including the same plant. This is preferably done byemasculating the male flowers of the first or second parent corn plant,(i.e., treating or manipulating the flowers so as to prevent pollenproduction, in order to produce an emasculated parent corn plant),Self-incompatibility systems are also used in some hybrid crops for thesame purpose. Self-incompatible plants still shed viable pollen and canpollinate plants of other varieties but are incapable of pollinatingthemselves or other plants of the same variety.

A fourth step comprises allowing cross-pollination to occur between thefirst and second parent corn plants. When the plants are not inpollinating proximity, this is done by placing a bag, usually paper orglassine, over the tassels of the first plant and another bag over thesilks of the incipient ear on the second plant. The bags are left inplace for at least 24 hours. Since pollen is viable for less than 24hours, this assures that the silks are not pollinated from other pollensources, that any stray pollen on the tassels of the first plant isdead, and that the only pollen transferred comes from the first plant.The pollen bag over the tassel of the first plant is then shakenvigorously to enhance release of pollen from the tassels, and the shootbag is removed from the silks of the incipient ear on the second plant.Finally, the pollen bag is removed from the tassel of the first plantand is placed over the silks of the incipient ear of the second plant,shaken again and left in place. Yet another step comprises harvestingthe seeds from at least one of the parent corn plants. The harvestedseed can be grown to produce a corn plant or hybrid corn plant.

The present invention also provides corn seed and plants produced by aprocess that comprises crossing a first parent corn plant with a secondparent corn plant, wherein at least one of the first or second parentcorn plants is a plant of the variety designated I363128. In oneembodiment of the invention, corn seed and plants produced by theprocess are first generation (F₁) hybrid corn seed and plants producedby crossing an inbred in accordance with the invention with another,distinct inbred. The present invention further contemplates seed of anF₁ hybrid corn plant. Therefore, certain exemplary embodiments of theinvention provide an F₁ hybrid corn plant and seed thereof.

In still yet another aspect of the invention, the genetic complement ofthe corn plant variety designated I363128 is provided. The phrase“genetic complement” is used to refer to the aggregate of nucleotidesequences, the expression of which sequences defines the phenotype of,in the present case, a corn plant, or a cell or tissue of that plant. Agenetic complement thus represents the genetic make up of an inbredcell, tissue or plant, and a hybrid genetic complement represents thegenetic make up of a hybrid cell, tissue or plant. The invention thusprovides corn plant cells that have a genetic complement in accordancewith the inbred corn plant cells disclosed herein, and plants, seeds anddiploid plants containing such cells.

Plant genetic complements may be assessed by genetic marker profiles,and by the expression of phenotypic traits that are characteristic ofthe expression of the genetic complement, e.g., isozyme typing profiles.Thus, such corn plant cells may be defined as having an SSR profile inaccordance with the profile shown in Table 6, or a genetic isozymetyping profile in accordance with the profile shown in Table 7, orhaving both an SSR profile and an isozyme typing profile in accordancewith the profiles shown in Table 6 and Table 7. It is understood thatvariety I363128 could also be identified by other types of geneticmarkers such as, for example, Simple Sequence Length Polymorphisms(SSLPs) (Williams et al., 1990), Randomly Amplified Polymorphic DNAs(RAPDs), DNA Amplification Fingerprinting (DAF), Sequence CharacterizedAmplified Regions (SCARs), Arbitrary Primed Polymerase Chain Reaction(AP-PCR), Amplified Fragment Length Polymorphisms (AFLPs) (EP 534 858,specifically incorporated herein by reference in its entirety), andSingle Nucleotide Polymorphisms (SNPs) (Wang et al., 1998).

In still yet another aspect, the present invention provides hybridgenetic complements, as represented by corn plant cells, tissues,plants, and seeds, formed by the combination of a haploid geneticcomplement of an inbred corn plant of the invention with a haploidgenetic complement of a second corn plant, preferably, another, distinctinbred corn plant. In another aspect, the present invention provides acorn plant regenerated from a tissue culture that comprises a hybridgenetic complement of this invention.

In still yet another aspect, the present invention provides a method ofproducing an inbred corn plant derived from the corn variety I363128,the method comprising the steps of: (a) preparing a progeny plantderived from corn variety I363128, wherein said preparing comprisescrossing a plant of the corn variety I363128 with a second corn plant,and wherein a sample of the seed of corn variety I363128 has beendeposited under ATCC Accession No. PTA-4494; (b) crossing the progenyplant with itself or a second plant to produce a seed of a progeny plantof a subsequent generation; (c) growing a progeny plant of a subsequentgeneration from said seed of a progeny plant of a subsequent generationand crossing the progeny plant of a subsequent generation with itself ora second plant; and (d) repeating steps (c) and (d) for an addition 3-10generations to produce an inbred corn plant derived from the cornvariety I363128. In the method, it may be desirable to select particularplants resulting from step (c) for continued crossing according to steps(b) and (c). By selecting plants having one or more desirable traits, aninbred corn plant derived from the corn variety I363128 is obtainedwhich possesses some of the desirable traits of corn variety I363128 aswell potentially other selected traits.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions of PlantCharacteristics

Barren Plants: Plants that are barren, i.e., lack an ear with grain, orhave an ear with only a few scattered kernels.

Cg: Colletotrichum graminicola rating. Rating times 10 is approximatelyequal to percent total plant infection.

CLN: Corn Lethal Necrosis (combination of Maize Chlorotic Mottle Virusand Maize Dwarf Mosaic virus) rating: numerical ratings are based on aseverity scale where 1=most resistant to 9=susceptible.

Cn: Corynebacterium nebraskense rating. Rating times 10 is approximatelyequal to percent total plant infection.

Cz: Cercospora zeae-maydis rating. Rating times 10 is approximatelyequal to percent total plant infection.

Dgg: Diatraea grandiosella girdling rating (values are percent plantsgirdled and stalk lodged).

Dropped Ears: Ears that have fallen from the plant to the ground.

Dsp: Diabrotica species root ratings (1=least affected to 9=severepruning).

Ear-Attitude: The attitude or position of the ear at harvest scored asupright, horizontal, or pendant.

Ear-Cob Color: The color of the cob, scored as white, pink, red, orbrown.

Ear-Cob Diameter: The average diameter of the cob measured at themidpoint.

Ear-Cob Strength: A measure of mechanical strength of the cobs tobreakage, scored as strong or weak.

Ear-Diameter: The average diameter of the ear at its midpoint.

Ear-Dry Husk Color: The color of the husks at harvest scored as buff,red, or purple.

Ear-Fresh Husk Color: The color of the husks 1 to 2 weeks afterpollination scored as green, red, or purple.

Ear-Husk Bract: The length of an average husk leaf scored as short,medium, or

Ear-Husk Cover: The average distance from the tip of the ear to the tipof the husks. Minimum value no less than zero.

Ear-Husk Opening: An evaluation of husk tightness at harvest scored astight, intermediate, or open.

Ear-Length: The average length of the ear.

Ear-Number Per Stalk: The average number of ears per plant.

Ear-Shank Internodes: The average number of internodes on the ear shank.

Ear-Shank Length: The average length of the ear shank.

Ear-Shelling Percent: The average of the shelled grain weight divided bythe sum of the shelled grain weight and cob weight for a single ear.

Ear-Silk Color: The color of the silk observed 2 to 3 days after silkemergence scored as green-yellow, yellow, pink, red, or purple.

Ear-Taper (Shape): The taper or shape of the ear scored as conical,semi-conical, or cylindrical.

Ear-Weight: The average weight of an ear.

Early Stand: The percent of plants that emerge from the ground asdetermined in the early spring.

ER: Ear rot rating (values approximate percent ear rotted).

Final Stand Count: The number of plants just prior to harvest.

GDUs: Growing degree units which are calculated by the Barger Method,where the heat units for a 24-h period are calculated as GDUs=[(Maximumdaily temperature+Minimum daily temperature)/2]−50. The highest maximumdaily temperature used is 86° F. and the lowest minimum temperature usedis 50° F.

GDUs to Shed: The number of growing degree units (GDUs) or heat unitsrequired for an inbred line or hybrid to have approximately 50% of theplants shedding pollen as measured from time of planting. GDUs to shedis determined by summing the individual GDU daily values from plantingdate to the date of 50% pollen shed.

GDUs to Silk: The number of growing degree units for an inbred line orhybrid to have approximately 50% of the plants with silk emergence asmeasured from time of planting, GDUs to silk is determined by summingthe individual GDU daily values from, planting date to the date of 50%silking.

Hc2: Helminthosporium carbonum race 2 rating. Rating times 10 isapproximately equal to percent total plant infection.

Hc3: Heiminthosporium carbonum race 3 rating. Rating times 10 isapproximately equal to percent total plant infection.

Hm: Helminthosporium maydis race 0 rating. Rating times 10 isapproximately equal to percent total plant infection.

Ht1: Helminthosporium turcicum race 1 rating. Rating times 10 isapproximately equal to percent total plant infection.

Ht2: Helminthosporium turcicum race 2 rating. Rating times 10 isapproximately equal to percent total plant infection.

HtG: Chlorotic-lesion type resistance. +=indicates the presence of Htchlorotic-lesion type resistance; −=indicates absence of Htchlorotic-lesion type resistance; and +/−=indicates segregation of Htchlorotic-lesion type resistance. Rating times 10 is approximately equalto percent total plant infection.

Kernel-Aleurone Color: The color of the aleurone scored as white, pink,tan, brown, bronze, red, purple, pale purple, colorless, or variegated.

Kernel-Cap Color: The color of the kernel cap observed at dry stage,scored as white, lemon-yellow, yellow, or orange.

Kernel-Endosperm Color: The color of the endosperm scored as white, paleyellow, or yellow.

Kernel-Endosperm Type: The type of endosperm scored as normal, waxy, oropaque.

Kernel-Grade: The percent of kernels that are classified as rounds.

Kernel-Length: The average distance from the cap of the kernel to thepedicel.

Kernel-Number Per Row: The average number of kernels in a single row.

Kernel-Pericarp Color: The color of the pericarp scored as colorless,red-white crown, tan, bronze, brown, light red, cherry red, orvariegated.

Kernel-Row Direction: The direction of the kernel rows on the ear scoredas straight, slightly curved, spiral, or indistinct (scattered).

Kernel-Row Number: The average number of rows of kernels on a singleear.

Kernel-Side Color: The color of the kernel side observed at the drystage, scored as white, pale yellow, yellow, orange, red, or brown.

Kernel-Thickness: The distance across the narrow side of the kernel.

Kernel-Type: The type of kernel scored as dent, flint, or intermediate.

Kernel-Weight: The average weight of a predetermined number of kernels.

Kernel-Width: The distance across the flat side of the kernel.

Kz: Kabatiella zeae rating. Rating times 10 is approximately equal topercent total plant infection.

Leaf-Angle: Angle of the upper leaves to the stalk scored as upright (0to 30 degrees), intermediate (30 to 60 degrees), or lax (60 to 90degrees).

Leaf-Color: The color of the leaves 1 to 2 weeks after pollinationscored as light green, medium green, dark green, or very dark green.

Leaf-Length: The average length of the primary ear leaf.

Leaf-Longitudinal Creases: A rating of the number of longitudinalcreases on the leaf surface 1 to 2 weeks after pollination. Creases arescored as absent, few, or many.

Leaf-Marginal Waves: A rating of the waviness of the leaf margin 1 to 2weeks after pollination. Rated as none, few, or many.

Leaf-Number: The average number of leaves of a mature plant. Countingbegins with the cotyledonary leaf and ends with the flag leaf.

Leaf-Sheath Anthocyanin: A rating of the level of anthocyanin in theleaf sheath 1 to 2 weeks after pollination, scored as absent,basal-weak, basal-strong, weak or strong.

Leaf-Sheath Pubescence: A rating of the pubescence of the leaf sheath.Ratings are taken 1 to 2 weeks after pollination and scored as light,medium or heavy.

Leaf-Width: The average width of the primary ear leaf measured at itswidest point.

LSS: Late season standability (values times 10 approximate percentplants lodged in disease evaluation plots).

Moisture: The moisture of the grain at harvest.

On1: Ostrinia nubilalis 1st brood rating (1=resistant to 9=susceptible).

On2: Ostrinia nubilalis 2nd brood rating (1=resistant to 9=susceptible).

Relative Maturity: A maturity rating based on regression analysis. Theregression analysis is developed by utilizing check hybrids and theirpreviously established day rating versus actual harvest moistures.Harvest moisture on the hybrid in question is determined and thatmoisture value is inserted into the regression equation to yield arelative maturity.

Root Lodging: Root lodging is the percentage of plants that root lodge.A plant is counted as root lodged if a portion of the plant leans fromthe vertical axis by approximately 30 degrees or more.

Seedling Color: Color of leaves at the 6 to 8 leaf stage.

Seedling Height: Plant height at the 6 to 8 leaf stage.

Seedling Vigor: A visual rating of the amount of vegetative growth on a1 to 9 scale, where 1 equals best. The score is taken when the averageentry in a trial is at the fifth leaf stage.

Selection Index: The selection index gives a single measure of hybrid'sworth based on information from multiple traits. One of the traits thatis almost always included is yield. Traits may be weighted according tothe level of importance assigned to them.

Sr: Sphacelotheca reiliana rating is actual percent infection.

Stalk-Anthocyanin: A rating of the amount of anthocyanin pigmentation inthe stalk. The stalk is rated 1 to 2 weeks after pollination as absent,basal-weak, basal-strong, weak, or strong.

Stalk-Brace Root Color: The color of the brace roots observed 1 to 2weeks after pollination as green, red, or purple.

Stalk-Diameter: The average diameter of the lowest visible internode ofthe stalk.

Stalk-Ear Height: The average height of the ear measured from the groundto the point of attachment of the ear shank of the top developed ear tothe stalk.

Stalk-Internode Direction: The direction of the stalk internode observedafter pollination as straight or zigzag.

Stalk-Internode Length: The average length of the internode above theprimary ear.

Stalk Lodging: The percentage of plants that did stalk lodge. Plants arecounted as stalk lodged if the plant is broken over or off below theear.

Stalk-Nodes With Brace Roots: The average number of nodes having braceroots per plant.

Stalk-Plant Height: The average height of the plant as measured from thesoil to the tip of the tassel.

Stalk-Tillers: The percent of plants that have tillers. A tiller isdefined as a secondary shoot that has developed as a tassel capable ofshedding pollen.

Staygreen: Staygreen is a measure of general plant health near the timeof black layer formation (physiological maturity). It is usuallyrecorded at the time the ear husks of most entries within a trial haveturned a mature color. Scoring is on a 1 to 9 basis where 1 equals best.

STR: Stalk rot rating (values represent severity rating of 1=25% ofinoculated internode rotted to 9=entire stalk rotted and collapsed).

SVC: Southeastern Virus Complex (combination of Maize Chlorotic DwarfVirus and Maize Dwarf Mosaic Virus) rating; numerical ratings are basedon a severity scale where 1 =most resistant to 9=susceptible (1988reactions are largely Maize Dwarf Mosaic Virus reactions).

Tassel-Anther Color: The color of the anthers at 50% pollen shed scoredas green-yellow, yellow, pink, red, or purple.

Tassel-Attitude: The attitude of the tassel after pollination scored asopen or compact.

Tassel-Branch Angle: The angle of an average tassel branch to the mainstem of the tassel scored as upright (less than 30 degrees),intermediate (30 to 45 degrees), or lax (greater than 45 degrees).

Tassel-Branch Number: The average number of primary tassel branches.

Tassel-Glume Band: The closed anthocyanin band at the base of the glumescored as present or absent.

Tassel-Glume Color: The color of the glumes at 50% shed scored as green,red, or purple.

Tassel-Length: The length of the tassel measured from the base of thebottom tassel branch to the tassel tip.

Tassel-Peduncle Length: The average length of the tassel peduncle,measured from the base of the flag leaf to the base of the bottom tasselbranch.

Tassel-Pollen Shed: A visual rating of pollen shed determined by tappingthe tassel and observing the pollen flow of approximately five plantsper entry. Rated on a 1 to 9 scale where 9=sterile, 1=most pollen.

Tassel-Spike Length: The length of the spike measured from the base ofthe top tassel branch to the tassel tip.

Test Weight: Weight of the grain in pounds for a given volume (bushel)adjusted to 15.5% moisture.

Yield: Yield of grain at harvest adjusted to 15.5% moisture.

II. Other Definitions

Allele: Any of one or more alternative forms of a gene locus, all ofwhich alleles relate to one trait or characteristic. In a diploid cellor organism, the two alleles of a given gene occupy corresponding locion a pair of homologous chromosomes.

Backcrossing: A process in which a breeder repeatedly crosses hybridprogeny back to one of the parents, for example, a first generationhybrid (F₁) with one of the parental genotypes of the F₁ hybrid.

Chromatography: A technique wherein a mixture of dissolved substancesare bound to a solid support followed by passing a column of fluidacross the solid support and varying the composition of the fluid. Thecomponents of the mixture are separated by selective elution.

Crossing: The pollination of a female flower of a corn plant, therebyresulting in the production of seed from the flower.

Cross-pollination: Fertilization by the union of two gametes fromdifferent plants.

Diploid: A cell or organism having two sets of chromosomes.

Electrophoresis: A process by which particles suspended in a fluid or agel matrix are moved under the action of an electrical field, andthereby separated according to their charge and molecular weight. Thismethod of separation is well known to those skilled in the art and istypically applied to separating various forms of enzymes and of DNAfragments produced by restriction endonucleases.

Emasculate: The removal of plant male sex organs or the inactivation ofthe organs with a chemical agent or a cytoplasmic or nuclear geneticfactor conferring male sterility.

Enzymes: Molecules which can act as catalysts in biological reactions.

F₁ Hybrid: The first generation progeny of the cross of two plants.

Genetic Complement: An aggregate of nucleotide sequences, the expressionof which sequences defines the phenotype in corn plants, or componentsof plants including cells or tissue.

Genotype: The genetic constitution of a cell or organism.

Haploid: A cell or organism having one set of the two sets ofchromosomes in a diploid.

Isozymes: Detectable variants of an enzyme, the variants catalyzing thesame reaction(s) but differing from each other, e.g., in primarystructure and/or electrophoretic mobility. The differences betweenisozymes are under single gene, codominant control. Consequently,electrophoretic separation to produce band patterns can be equated todifferent alleles at the DNA level. Structural differences that do notalter charge cannot be detected by this method.

Isozyme typing profile: A profile of band patterns of isozymes separatedby electrophoresis that can be equated to different alleles at the DNAlevel.

Linkage: A phenomenon wherein alleles on the same chromosome tend tosegregate together more often than expected by chance if theirtransmission was independent.

Marker: A readily detectable phenotype, preferably inherited incodominant fashion (both alleles at a locus in a diploid heterozygoteare readily detectable), with no environmental variance component, i.e.,heritability of 1.

I363128: The corn plant variety from which seeds having ATCC AccessionNo. PTA-4494 were obtained, as well as plants grown from those seeds.

Phenotype: The detectable characteristics of a cell or organism, whichcharacteristics are the manifestation of gene expression.

Quantitative Trait Loci (QTL): Genetic loci that contribute, at least inpart, certain numerically representable traits that are usuallycontinuously distributed.

Regeneration: The development of a plant from tissue culture.

SSR profile: A profile of simple sequence repeats used as geneticmarkers and scored by gel electrophoresis following PCR™ amplificationusing flanking oligonucleotide primers.

Self-pollination: The transfer of pollen from the anther to the stigmaof the same plant.

Single Locus Converted (Conversion) Plant: Plants which are developed bya plant breeding technique called backcrossing wherein essentially allof the desired morphological and physiological characteristics of aninbred are recovered in addition to the characteristics conferred by thesingle locus transferred into the inbred via the backcrossing technique.A single locus may comprise one gene, or in the case of transgenicplants, one or more transgenes integrated into the host genome at asingle site (locus).

Tissue Culture: A composition comprising isolated cells of the same or adifferent type or a collection of such cells organized into parts of aplant.

Transgene: A genetic sequence which has been introduced into the nuclearor chloroplast genome of a maize plant by a genetic transformationtechnique.

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples that follow representtechniques discovered by the inventor to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments that are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

III. Inbred Corn Plant I363128

In accordance with one aspect of the present invention, there isprovided a novel inbred corn plant variety designated I363128. Inbredcorn plant I363128 can be compared to inbred corn plants I244339 andI465846. I363128 differs significantly (at the 1%, 5%, or 10% level)from these inbred lines in several aspects (Table 1 and Table 2).

TABLE 1 Comparison of I363128 with I244339 I363128 I244339 DIFF P VALUEEHT INCH 38.7 34.7 4.0 0.518 FINAL 61.6 64.2 −2.6 0.596 MST % 18.4 17.31.1 0.853 PHT INCH 91.4 84.6 6.8 0.296 RTL % 2.0 5.7 −3.7 0.005* SHEDGDU 1453.6 1468.7 −15.1 0.942 SILK GDU 1515.0 1498.4 16.6 0.740 STL %1.9 2.9 −1.0 0.461 YLD BU/A 63.0 76.4 −13.4 0.554 Significance Levelsare indicated as: + = 10%, * = 5%, ** = 1%. Legend Abbreviations: EHTINCH = Ear Height (inches) FINAL = Final Stand MST % = Moisture(percent) PHT INCH = Plant Height (inches) RTL % = Root Lodging(percent) SHED GDU = GDUs to Shed SILK GDU = GDUs to Silk STL % = StalkLodging (percent) YLD BU/A = Yield (bushels/acre)

TABLE 2 Comparison of I363128 with I465846 I363128 I465846 DIFF P VALUEEHT INCH 38.7 36.1 2.6 0.544 FINAL 61.6 57.4 4.2 0.207 MST % 18.4 16.51.9 0.816 PHT INCH 91.4 89.4 2.0 0.247 SHED GDU 1453.6 1486.4 −32.80.901 SILK GDU 1515.0 1511.5 3.5 0.899 STL % 1.9 1.3 0.6 0.328 YLD BU/A63.0 52.8 10.2 0.058+ Significance Levels are indicated as: + = 10%, * =5%, ** = 1%. Legend Abbreviations: EHT INCH = Ear Height (inches) FINAL= Final Stand MST % = Moisture (percent) PHT INCH = Plant Height(inches) SHED GDU = GDUs to Shed SILK GDU = GDUs to Silk STL % = StalkLodging (percent) YLD BU/A = Yield (bushels/acre)

A. Origin and Breeding History

Inbred plant I363128 was derived from a cross between the lines BN399Aand FR810W. The origin and breeding history of I363128 can be summarizedas follows:

Summer 1994 Inbred line BN399A was crossed to FR810W (row 94.1880 X row94.1875).

Winter 1994-95 F1 seed was grown and self-pollinated (rows 94.104 &94.247). A bulk was made on each row.

Summer 1995 F2 seed was grown and self-pollinated (rows 95.805 to95.816). 47 ears were selected.

Winter 1996 Selected ears of the F3 seed (based on 1996 yield trials)were grown ear-to-row and self-pollinated (rows 96H.HC14.12 to96H.HC14.16). 3 ears were harvested from row 96H.HC14.14 and this rowwas given the code I363128.

Summer 1997 F4 seed was grown for observation.

Winter 1997-98 F4 seed was grown ear-to-row and self-pollinated (rows97H.11X08.16 to 97H.11X08.18). 4 ears were selected from row97H.11X08.16.

Summer 1998 F5 seed was grown ear-to-row and self-pollinated (rows98.3181 to 98.3193 and 98.5057 to 98.5059) F6 seed from row 98.3181 wasbulked.

Winter 1998-99 F6 seed was grown and self-pollinated (rows 98F.SL.957 to98F.SL.960).

Corn variety I363128 shows uniformity and stability within the limits ofenvironmental influence for the traits described hereinafter in Table 3.I363128 has been self-pollinated and ear-rowed a sufficient number ofgenerations with careful attention paid to uniformity of plant type toensure homozygosity and phenotypic stability. No variant traits havebeen observed or are expected in I363128.

Inbred corn plants can be reproduced by planting the seeds of the inbredcorn plant I363128, growing the resulting corn plants underself-pollinating or sib-pollinating conditions with adequate isolationusing standard techniques well known to an artisan skilled in theagricultural arts. Seeds can be harvested from such a plant usingstandard, well known procedures.

B. Phenotypic Description

In accordance with another aspect of the present invention, there isprovided a corn plant having the physiological and morphologicalcharacteristics of corn plant I363128. A description of selectedphysiological and morphological characteristics of corn plant I363128 ispresented in Table 3.

TABLE 3 Morphological Traits for the Corn Variety I363128 andComparative Varieties VALUE CHARACTERISTIC I363128 I244339 I465846 1.STALK Diameter (width)  1.8  1.7  1.8 cm. Anthocyanin Absent AbsentAbsent Brace Root Color Moderate Absent Strong Nodes With  1.5  2.1  1.0Brace Roots Internode Straight Straight Straight Direction InternodeLength 14.9 13.4 12.0 cm. 2. LEAF Color Light Green Green Green Lengthcm. 63.0 73.0 67.0 Width cm.  9.1  9.2  9.2 Sheath Antho- Absent FaintAbsent cyanin Sheath None Moderate None Pubescence Marginal WavesModerate Few Few Longitudinal Moderate Moderate Moderate Creases 3.TASSEL Length cm. 42.0 45.0 43.0 Spike Length cm. 31.0 36.0 29.0Peduncle Length  7.0  9.0  9.0 cm. Branch Number  1.8  4.2  2.0 AntherColor Green-Yellow Light Green Green-Yellow Glume Color Green LightGreen Green Glume Band Absent Absent Absent 4. EAR Silk Color Red YellowRed Number Per Stalk  1.0  2.0  1.0 Position (attitude) HorizontalPendent Horizontal Length cm. 15.3 15.1 11.8 Shape Semi-ConicalSemi-Conical Semi-Conical Diameter cm.  4.0  4.0  3.8 Shank Length cm. 8.4  8.1 11.8 Husk Bract Short Short Short Husk Cover cm.  3.1  5.2 1.9 Husk Opening Intermediate Intermediate Intermediate Husk ColorFresh Green Green Green Husk Color Dry Buff Buff Buff Cob Diameter  2.3 2.3  2.1 cm. Cob Color White White White Shelling Percent 78.7 86.377.9 5. KERNEL Row Number 13.2 14.0 11.2 Number Per Row 32.6 30.8 30.0Row Direction Straight Straight Straight Type Normal Normal Normal CapColor White White White Side Color White White White Length (depth) 10.0 9.7 10.2 mm. Width mm.  7.9  7.8  8.7 Thickness  4.5  4.7  5.0Endosperm Type Normal Normal Normal Endosperm Color White White White*These are typical values. Values may vary due to environment. Othervalues that are substantially equivalent are also within the scope ofthe invention. Substantially equivalent refers to quantitative traitsthat when compared do not show statistical differences of their means.

C. Deposit Information

A representative deposit of 2500 seeds of the inbred corn varietydesignated I363128 has been made with the American Type CultureCollection (ATCC), 10801 University Blvd., Manassas, Va. on Jun. 25,2002. Those deposited seeds have been assigned ATCC Accession No.PTA4494. The deposit was made in accordance with the terms andprovisions of the Budapest Treaty relating to deposit of microorganismsand was made for a term of at least thirty (30) years and at least five(05) years after the most recent request for the furnishing of a sampleof the deposit is received by the depository, or for the effective termof the patent, whichever is longer, and will be replaced if it becomesnon-viable during that period.

IV. Single Locus Conversions

When the term inbred corn plant is used in the context of the presentinvention, this also includes any single locus conversions of thatinbred. The term single locus converted plant as used herein refers tothose corn plants which are developed by a plant breeding techniquecalled backcrossing wherein essentially all of the desired morphologicaland physiological characteristics of an inbred are recovered in additionto the single locus transferred into the inbred via the backcrossingtechnique. Backcrossing methods can be used with the present inventionto improve or introduce a characteristic into the inbred. The termbackcrossing as used herein refers to the repeated crossing of a hybridprogeny back to one of the parental corn plants for that inbred. Theparental corn plant which contributes the locus or loci for the desiredcharacteristic is termed the nonrecurrent or donor parent. Thisterminology refers to the fact that the nonrecurrent parent is used onetime in the backcross protocol and therefore does not recur. Theparental corn plant to which the locus or loci from the nonrecurrentparent are transferred is known as the recurrent parent as it is usedfor several rounds in the backcrossing protocol (Poehlman et al., 1995;Fehr, 1987; Sprague and Dudley, 1988). In a typical backcross protocol,the original inbred of interest (recurrent parent) is crossed to asecond inbred (nonrecurrent parent) that carries the single locus ofinterest to be transferred. The resulting progeny from this cross arethen crossed again to the recurrent parent and the process is repeateduntil a corn plant is obtained wherein essentially all of the desiredmorphological and physiological characteristics of the recurrent parentare recovered in the converted plant, in addition to the singletransferred locus from the nonrecurrent parent. The backcross processmay be accelerated by the use of genetic markers, such as SSR, RFLP, SNPor AFLP markers to identify plants with the greatest genetic complementfrom the recurrent parent.

The selection of a suitable recurrent parent is an important step for asuccessful backcrossing procedure. The goal of a backcross protocol isto alter or substitute a single trait or characteristic in the originalinbred. To accomplish this, a single locus of the recurrent inbred ismodified or substituted with the desired locus from the nonrecurrentparent, while retaining essentially all of the rest of the desiredgenetic, and therefore the desired physiological and morphologicalconstitution of the original inbred. The choice of the particularnonrecurrent parent will depend on the purpose of the backcross; one ofthe major purposes is to add some commercially desirable, agronomicallyimportant trait to the plant. The exact backcrossing protocol willdepend on the characteristic or trait being altered to determine anappropriate testing protocol. Although backcrossing methods aresimplified when the characteristic being transferred is a dominantallele, a recessive allele may also be transferred. In this instance itmay be necessary to introduce a test of the progeny to determine if thedesired characteristic has been successfully transferred.

Many single locus traits have been identified that are not regularlyselected for in the development of a new inbred but that can be improvedby backcrossing techniques. Single locus traits may or may not betransgenic; examples of these traits include, but are not limited to,male sterility, waxy starch, herbicide resistance, resistance forbacterial, final, or viral disease, insect resistance, male fertility,enhanced nutritional quality, industrial usage, yield stability, andyield enhancement. These genes are generally inherited through thenucleus, but may be inherited through the cytoplasm. Some knownexceptions to this are genes for male sterility, some of which areinherited cytoplasmically, but still act as single locus traits. Anumber of exemplary single locus traits are described in, for example,PCT Application WO 95/06128, including an ALS gene conferring resistanceto sulfonylurea, the disclosure of which is specifically incorporatedherein by reference.

Examples of genes conferring male sterility include those disclosed inU.S. Pat. Nos. 3,861,709, 3,710,511, 4,654,465, 5,625,132, and4,727,219, each of the disclosures of which are specificallyincorporated herein by reference in their entirety. A particularlyuseful type of male sterility gene is one which can be induced byexposure to a chemical agent, for example, a herbicide (U.S. Pat. Ser.No. 08/927,368, filed Sep. 11, 1997, the disclosure of which isspecifically incorporated herein by reference in its entirety). Bothinducible and non-inducible male sterility genes can increase theefficiency with which hybrids are made, in that they eliminate the needto physically emasculate the corn plant used as a female in a givencross.

Where one desires to employ male-sterility systems with a corn plant inaccordance with the invention, it may be beneficial to also utilize oneor more male-fertility restorer genes. For example, where cytoplasmicmale sterility (CMS) is used, hybrid seed production requires threeinbred lines: (1) a cytoplasmically male-sterile line having a CMScytoplasm; (2) a fertile inbred with normal cytoplasm, which is isogenicwith the CMS line for nuclear genes (“maintainer line”); and (3) adistinct, fertile inbred with normal cytoplasm, carrying a fertilityrestoring gene (“restorer” line). The CMS line is propagated bypollination with the maintainer line, with all of the progeny being malesterile, as the CMS cytoplasm is derived from the female parent. Thesemale sterile plants can then be efficiently employed as the femaleparent in hybrid crosses with the restorer line, without the need forphysical emasculation of the male reproductive parts of the femaleparent.

The presence of a male-fertility restorer gene results in the productionof fully fertile F₁ hybrid progeny. If no restorer gene is present inthe male parent, male-sterile hybrids are obtained. Such hybrids areuseful where the vegetative tissue of the corn plant is utilized, e.g.,for silage, but in most cases, the seeds will be deemed the mostvaluable portion of the crop, so fertility of the hybrids in these cropsmust be restored. Therefore, one aspect of the current inventionconcerns the inbred corn plant I363128 comprising a single gene capableof restoring male fertility in an otherwise male-sterile inbred orhybrid plant. Examples of male-sterility genes and correspondingrestorers which could be employed with the inbred of the invention arewell known to those of skill in the art of plant breeding and aredisclosed in, for instance, U.S. Pat. No. 5,530,191; U.S. Pat. Nos.5,689,041; 5,741,684; and 5,684,242, the disclosures of which are eachspecifically incorporated herein by reference in their entirety.

Direct selection may be applied where a single locus acts as a dominanttrait. An example of a dominant trait is the herbicide resistance trait.For this selection process, the progeny of the initial cross are sprayedwith the herbicide prior to the backcrossing. The spraying eliminatesany plants which do not have the desired herbicide resistancecharacteristic, and only those plants which have the herbicideresistance gene are used in the subsequent backcross. This process isthen repeated for all additional backcross generations.

Many useful single locus traits are those which are introduced bygenetic transformation techniques. Methods for the genetictransformation of maize are known to those of skill in the art. Forexample, methods which have been described for the genetictransformation of maize include electroporation (U.S. Pat. No.5,384,253), electrotransformation (U.S. Pat. No. 5,371,003),microprojectile bombardment (U.S. Pat. Nos. 5,550,318; 5,736,369,5,538,880; and PCT Publication WO 95/06128), Agrobacterium-mediatedtransformation (U.S. Pat. No. 5,591,616 and E.P. Publication EP672752),direct DNA uptake transformation of protoplasts (Omirulleh et al., 1993)and silicon carbide fiber-mediated transformation (U.S. Pat. Nos.5,302,532 and 5,464,765).

A type of single locus trait which can be introduced by genetictransformation (U.S. Pat. No. 5,554,798) and has particular utility is agene which confers resistance to the herbicide glyphosate. Glyphosateinhibits the action of the enzyme EPSPS, which is active in thebiosynthetic pathway of aromatic amino acids. Inhibition of this enzymeleads to starvation for the amino acids phenylalanine, tyrosine, andtryptophan and secondary metabolites derived therefrom. Mutants of thisenzymne are available which are resistant to glyphosate. For example,U.S. Pat. No. 4,535,060 describes the isolation of EPSPS mutations whichconfer glyphosate resistance upon organisms having the Salmonellatyphimurium gene for EPSPS, aroA. A mutant EPSPS gene having similarmutations has also been cloned from Zea mays. The mutant gene encodes aprotein with amino acid changes at residues 102 and 106 (PCT PublicationWO 97/04103). When a plant comprises such a gene, a herbicide resistantphenotype results.

Plants having inherited a transgene comprising a mutated EPSPS gene may,therefore, be directly treated with the herbicide glyphosate without theresult of significant damage to the plant. This phenotype providesfarmers with the benefit of controlling weed growth in a field of plantshaving the herbicide resistance trait by application of the broadspectrum herbicide glyphosate. For example, one could apply theherbicide ROUNDUP™, a commercial formulation of glyphosate manufacturedand sold by the Monsanto Company, over the top in fields whereglyphosate resistant corn plants are grown. The herbicide applicationrates may typically range from 4 ounces of ROUNDUP™ to 256 ouncesROUNDUP™ per acre. More preferably, about 16 ounces to about 64 ouncesper acre of ROUNDUP™ may be applied to the field. However, theapplication rate may be increased or decreased as needed, based on theabundance and/or type of weeds being treated. Additionally, depending onthe location of the field and weather conditions, which will influenceweed growth and the type of weed infestation, it may be desirable toconduct further glyphosate treatments. The second glyphosate applicationwill also typically comprise an application rate of about 16 ounces toabout 64 ounces of ROUNDUP™ per acre treated. Again, the treatment ratemay be adjusted based on field conditions. Such methods of applicationof herbicides to agricultural crops are well known in the art and aresummarized in general in Anderson (1983).

Alternatively, more than one single locus trait may be introgressed intoan elite inbred by the method of backcross conversion. A selectablemarker gene and a gene encoding a protein which confers a trait ofinterest may be simultaneously introduced into a maize plant as a resultof genetic transformation. Usually one or more introduced genes willintegrate into a single chromosome site in the host cell's genome. Forexample, a selectable marker gene encoding phosphinothricin acetyltransferase (PPT) (e.g., a bar gene) and conferring resistance to theactive ingredient in some herbicides by inhibiting glutamine synthetase,and a gene encoding an endotoxin from Bacillus thuringiensis (Bt) andconferring resistance to particular classes of insects, e.g.,lepidopteran insects, in particular the European Corn Borer, may besimultaneously introduced into a host genome. Furthermore, through theprocess of backcross conversion more than one transgenic trait may betransferred into an elite inbred.

The waxy characteristic is an example of a recessive trait. In thisexample, the progeny resulting from the first backcross generation (BC1)must be grown and selfed. A test is then run on the selfed seed from theBC1 plant to determine which BC1 plants carried the recessive gene forthe waxy trait. In other recessive traits additional progeny testing,for example growing additional generations such as the BC1S1, may berequired to determine which plants carry the recessive gene.

V. Origin and Breeding History of an Exemplary Single Locus ConvertedPlant

85DGD1 MLms is a single locus conversion of 85DGD1 to cytoplasmic malesterility. 85DGD1 MLms was derived using backcross methods. 85DGD1 (aproprietary inbred of DEKALB Genetics Corporation) was used as therecurrent parent and MLms, a germplasm source carrying ML cytoplasmicsterility, was used as the nonrecurrent parent. The breeding history ofthe single locus converted inbred 85DGD1 MLms can be summarized asfollows:

Hawaii Nurseries Planting Date Apr. 02, 1992 Made up S-O: Female row 585male row 500

Hawaii Nurseries Planting Date Jul. 15, 1992 S-O was grown and plantswere backcrossed times 85DGD1 (rows 444′443)

Hawaii Nurseries Planting Date Nov. 18, 1992 Bulked seed of the BC1 wasgrown and backcrossed times 85DGD1 (rows V3-27 ′V3-26)

Hawaii Nurseries Planting Date Apr. 02, 1993 Bulked seed of the BC2 wasgrown and backcrossed times 85DGD1 (rows 37′36)

Hawaii Nurseries Planting Date Jul. 14, 1993 Bulked seed of the BC3 wasgrown and backcrossed times 85DGD1 (rows 99′98)

Hawaii Nurseries Planting Date Oct. 28, 1993 Bulked seed of BC4 wasgrown and backcrossed times 85DGD1 (rows KS-63′KS62)

Summer 1994 A single ear of the BC5 was grown and backcrossed times85DGD1 (MC94-822′MC94-822-7)

Winter 1994 Bulked seed of the BC6 was grown and backcrossed times85DGD1 (3Q-1′3Q-2)

Summer 1995 Seed of the BC7 was bulked and named 85DGD1 MLms.

VI. Tissue Cultures and in Viro Regeneration of Corn Plants

A further aspect of the invention relates to tissue cultures of the cornplant designated I363128. As used herein, the term “tissue culture”indicates a composition comprising isolated cells of the same or adifferent type or a collection of such cells organized into parts of aplant. Exemplary types of tissue cultures are protoplasts, calli andplant cells that are intact in plants or parts of plants, such asembryos, pollen, flowers, kernels, ears, cobs, leaves, husks, stalks,roots, root tips, anthers, silk, and the like. In a preferredembodiment, the tissue culture comprises embryos, protoplasts,meristematic cells, pollen, leaves or anthers derived from immaturetissues of these plant parts. Means for preparing and maintaining planttissue cultures are well known in the art (U.S. Pat. Nos. 5,538,880; and5,550,318, each incorporated herein by reference in their entirety). Byway of example, a tissue culture comprising organs such as tassels oranthers has been used to produce regenerated plants (U.S. Pat. Nos.5,445,961 and 5,322,789; the disclosures of which are incorporatedherein by reference).

VII. Tassel/Anther Culture

Tassels contain anthers which in turn enclose microspores. Microsporesdevelop into pollen. For anther/microspore culture, if tassels are theplant composition, they are preferably selected at a stage when themicrospores are uninucleate, that is, include only one, rather than 2 or3 nuclei. Methods to determine the correct stage are well known to thoseskilled in the art and include mitramycin fluorescent staining (Pace etal., 1987), trypan blue (preferred) and acetocarmine squashing. Themid-uninucleate microspore stage has been found to be the developmentalstage most responsive to the subsequent methods disclosed to ultimatelyproduce plants.

Although microspore-containing plant organs such as tassels cangenerally be pretreated at any cold temperature below about 25° C., arange of 4 to 25° C. is preferred, and a range of 8 to 14° C. isparticularly preferred. Although other temperatures yield embryoids andregenerated plants, cold temperatures produce optimum response ratescompared to pretreatment at temperatures outside the preferred range.Response rate is measured as either the number of embryoids or thenumber of regenerated plants per number of microspores initiated inculture. Exemplary methods of microspore culture are disclosed in, forexample, U.S. Pat. Nos. 5,322,789 and 5,445,961, the disclosures ofwhich are specifically incorporated herein by reference.

Although not required, when tassels are employed as the plant organ, itis generally preferred to sterilize their surface. Following surfacesterilization of the tassels, for example, with a solution of calciumhypochloride, the anthers are removed from about 70 to 150 spikelets(small portions of the tassels) and placed in a preculture orpretreatment medium. Larger or smaller amounts can be used depending onthe number of anthers.

When one elects to employ tassels directly, tassels are preferablypretreated at a cold temperature for a predefined time, preferably at10° C. for about 4 days. After pretreatment of a whole tassel at a coldtemperature, dissected anthers are further pretreated in an environmentthat diverts microspores from their developmental pathway. The functionof the preculture medium is to switch the developmental program from oneof pollen development to that of embryoid/calus development. Anembodiment of such an environment in the form of a preculture mediumincludes a sugar alcohol, for example mannitol or sorbitol, inositol orthe like. An exemplary synergistic combination is the use of mannitol ata temperature of about 10° C. for a period ranging from about 10 to 14days. In a preferred embodiment, 3 ml of 0.3 M mannitol combined with 50mg/l of ascorbic acid, silver nitrate, and colchicine is used forincubation of anthers at 10° C. for between 10 and 14 days. Anotherembodiment is to substitute sorbitol for mannitol. The colchicineproduces chromosome doubling at this early stage. The chromosomedoubling agent is preferably only present at the preculture stage.

It is believed that the mannitol or other similar carbon structure orenvironmental stress induces starvation and functions to forcemicrospores to focus their energies on entering developmental stages.The cells are unable to use, for example, mannitol as a carbon source atthis stage. It is believed that these treatments confuse the cellscausing them to develop as embryoids and plants from microspores.Dramatic increases in development from these haploid cells, as high as25 embryoids in 104 microspores, have resulted from using these methods.

In embodiments where microspores are obtained from anthers, microsporescan be released from the anthers into an isolation medium following themannitol preculture step. One method of release is by disruption of theanthers, for example, by chopping the anthers into pieces with a sharpinstrument, such as a razor blade, scalpel, or Waring blender. Theresulting mixture of released microspores, anther fragments, andisolation medium are then passed through a filter to separatemicrospores from anther wall fragments. An embodiment of a filter is amesh, more specifically, a nylon mesh of about 112 mm pore size. Thefiltrate which results from filtering the microspore-containing solutionis preferably relatively free of anther fragments, cell walls, and otherdebris.

In a preferred embodiment, isolation of microspores is accomplished at atemperature below about 25° C. and preferably, at a temperature of lessthan about 15° C. Preferably, the isolation media, dispersing tool(e.g., razor blade), funnels, centrifuge tubes, and dispersing container(e.g., petri dish) are all maintained at the reduced temperature duringisolation. The use of a precooled dispersing tool to isolate maizemicrospores has been reported (Gaillard et al., 1991).

Where appropriate and desired, the anther filtrate is then washedseveral times in isolation medium. The purpose of the washing andcentrifugation is to eliminate any toxic compounds which are containedin the non-microspore part of the filtrate and are created by thechopping process. The centrifugation is usually done at decreasing spinspeeds, for example, 1000, 750, and finally 500 rpms. The result of theforegoing steps is the preparation of a relatively pure tissue culturesuspension of microspores that are relatively free of debris and antherremnants.

To isolate microspores, an isolation media is preferred. An isolationmedia is used to separate microspores from the anther walls whilemaintaining their viability and embryogenic potential. An illustrativeembodiment of an isolation media includes a 6% sucrose or maltosesolution combined with an antioxidant such as 50 mg/l of ascorbic acid,0.1 mg/l biotin, and 400 mg/l of proline, combined with 10 mg/l ofnicotinic acid and 0.5 mg/l AgNO₃. In another embodiment, the biotin andproline are omitted.

An isolation media preferably has a higher antioxidant level where it isused to isolate microspores from a donor plant (a plant from which aplant composition containing a microspore is obtained) that is fieldgrown in contrast to greenhouse grown. A preferred level of ascorbicacid in an isolation medium is from about 50 mg/l to about 125 mg/l and,more preferably, from about 50 mg/l to about 100 mg/l.

One can find particular benefit in employing a support for themicrospores during culturing and subculturing. Any support thatmaintains the cells near the surface can be used. The microsporesuspension is layered onto a support, for example by pipetting. Thereare several types of supports which are suitable and are within thescope of the invention. An illustrative embodiment of a solid support isa TRANSWELL® culture dish. Another embodiment of a solid support fordevelopment of the microspores is a bilayer plate wherein liquid mediais on top of a solid base. Other embodiments include a mesh or amillipore filter. Preferably, a solid support is a nylon mesh in theshape of a raft. A raft is defined as an approximately circular supportmaterial which is capable of floating slightly above the bottom of atissue culture vessel, for example, a petri dish, of about a 60 or 100mm size, although any other laboratory tissue culture vessel willsuffice. In an illustrative embodiment, a raft is about 55 mm indiameter.

Culturing isolated microspores on a solid support, for example, on a 10mm pore nylon raft floating on 2.2 ml of medium in a 60 mm petri dish,prevents microspores from sinking into the liquid medium and thusavoiding low oxygen tension. These types of cell supports enable theserial transfer of the nylon raft with its associatedmicrospore/embryoids ultimately to full strength medium containingactivated charcoal and solidified with, for example, GELRITE™(solidifying agent). The charcoal is believed to absorb toxic wastes andintermediaries. The solid medium allows embryoids to mature.

The liquid medium passes through the mesh while the microspores areretained and supported at the medium-air interface. The surface tensionof the liquid medium in the petri dish causes the raft to float. Theliquid is able to pass through the mesh; consequently, the microsporesstay on top. The mesh remains on top of the total volume of liquidmedium. An advantage of the raft is to permit diffusion of nutrients tothe microspores. Use of a raft also permits transfer of the microsporesfrom dish to dish during subsequent subculture with minimal loss,disruption, or disturbance of the induced embryoids that are developing.The rafts represent an advantage over the multi-welled TRANSWELL®plates, which are commercially available from COSTAR, in that thecommercial plates are expensive. Another disadvantage of these plates isthat to achieve the serial transfer of microspores to subsequent media,the membrane support with cells must be peeled off the insert in thewells. This procedure does not produce as good a yield nor as efficienttransfers, as when a mesh is used as a vehicle for cell transfer.

The culture vessels can be further defined as either (1) a bilayer 60 mmpetri plate wherein the bottom 2 ml of medium are solidified with 0.7%agarose overlaid with 1 mm of liquid containing the microspores; (2) anylon mesh raft wherein a wafer of nylon is floated on 1.2 ml of mediumand 1 ml of isolated microspores is pipetted on top; or (3) TRANSWELL®plates wherein isolated microspores are pipetted onto membrane insertswhich support the microspores at the surface of 2 ml of medium.

After the microspores have been isolated, they are cultured in a lowstrength anther culture medium until about the 50 cell stage when theyare subcultured onto an embryoid/callus maturation medium. Medium isdefined at this stage as any combination of nutrients that permit themicrospores to develop into embryoids or callus. Many examples ofsuitable embryoid/callus promoting media are well known to those skilledin the art. These media will typically comprise mineral salts, a carbonsource, vitamins, and growth regulators. A solidifying agent isoptional. A preferred embodiment of such a media is referred to as “Dmedium,” which typically includes 6N1 salts, AgNO₃ and sucrose ormaltose.

In an illustrative embodiment, 1 ml of isolated microspores are pipettedonto a 10 mm nylon raft and the raft is floated on 1.2 ml of medium “D,”containing sucrose or preferably maltose. Both calli and embryoids candevelop. Calli are undifferentiated aggregates of cells. Type I is arelatively compact, organized, and slow growing callus. Type II is asoft, friable, and fast-growing one. Embryoids are aggregates exhibitingsome embryo-like structures. The embryoids are preferred for subsequentsteps to regenerating plants. Culture medium “D” is an embodiment ofmedium that follows the isolation medium and replaces it. Medium “D”promotes growth to an embryoid/callus. This medium comprises 6N1 saltsat ⅛ the strength of a basic stock solution (major components) and minorcomponents, plus 12% sucrose, or preferably 12% maltose, 0.1 mg/l B1,0.5 mg/l nicotinic acid, 400 mg/l proline and 0.5 mg/l silver nitrate.Silver nitrate is believed to act as an inhibitor to the action ofethylene. Multi-cellular structures of approximately 50 cells eachgenerally arise during a period of 12 days to 3 weeks. Serial transferafter a two week incubation period is preferred.

After the petri dish has been incubated for an appropriate period oftime, preferably two weeks in the dark at a predefined temperature, araft bearing the dividing microspores is transferred serially to solidbased media which promote embryo maturation. In an illustrativeembodiment, the incubation temperature is 30° C. and the mesh raftsupporting the embryoids is transferred to a 100 mm petri dishcontaining the 6N1-TGR-4P medium, an “anther culture medium.” Thismedium contains 6N1 salts, supplemented with 0.1 mg/l TIBA, 12% sugar(sucrose, maltose, or a combination thereof), 0.5% activated charcoal,400 mg/l proline, 0.5 mg/l B, 0.5 mg/l nicotinic acid, and 0.2 percentGELRITE™ (solidifying agent) and is capable of promoting the maturationof the embryoids. Higher quality embryoids, that is, embryoids whichexhibit more organized development, such as better shoot meristemformation without precocious germination, were typically obtained withthe transfer to full strength medium compared to those resulting fromcontinuous culture using only, for example, the isolated microsporeculture (IMC) Medium “D.” The maturation process permits the pollenembryoids to develop further in route toward the eventual regenerationof plants. Serial transfer occurs to full strength solidified 6N1 mediumusing either the nylon raft, the TRANSWELL® membrane, or bilayer plates,each one requiring the movement of developing embryoids to permitfurther development into physiologically more mature structures. In anespecially preferred embodiment, microspores are isolated in anisolation media comprising about 6% maltose, cultured for about twoweeks in an embryoid/calli induction medium comprising about 12% maltoseand then transferred to a solid medium comprising about 12% sucrose.

At the point of transfer of the raft, after about two weeks ofincubation, embryoids exist on a nylon support. The purpose oftransferring the raft with the embryoids to a solidified medium afterthe incubation is to facilitate embryo maturation. Mature embryoids atthis point are selected by visual inspection indicated by zygoticembryo-like dimensions and structures and are transferred to the shootinitiation medium. It is preferred that shoots develop before roots, orthat shoots and roots develop concurrently. If roots develop beforeshoots, plant regeneration can be impaired. To produce solidified media,the bottom of a petri dish of approximately 100 mm is covered with about30 ml of 0.2% GELRITE® solidified medium. A sequence of regenerationmedia are used for whole plant formation from the embryoids.

During the regeneration process, individual embryoids are induced toform plantlets. The number of different media in the sequence can varydepending on the specific protocol used. Finally, a rooting medium isused as a prelude to transplanting to soil. When plantlets reach aheight of about 5 cm, they are then transferred to pots for furthergrowth into flowering plants in a greenhouse by methods well known tothose skilled in the art.

Plants have been produced from isolated microspore cultures by themethods disclosed herein, including self-pollinated plants. The rate ofembryoid induction was much higher with the synergistic preculturetreatment consisting of a combination of stress factors, including acarbon source which can be capable of inducing starvation, a coldtemperature, and colchicine, than has previously been reported. Anillustrative embodiment of the synergistic combination of treatmentsleading to the dramatically improved response rate compared to priormethods, is a temperature of about 10° C., mannitol as a carbon source,and 0.05% colchicine.

The inclusion of ascorbic acid, an anti-oxidant, in the isolation mediumis preferred for maintaining good microspore viability. However, thereseems to be no advantage to including mineral salts in the isolationmedium. The osmotic potential of the isolation medium was maintainedoptimally with about 6% sucrose, although a range of 2% to 12% is withinthe scope of this invention.

In an embodiment of the embryoid/callus organizing media, mineral saltsconcentration in IMC Culture Media “D” is (⅛×), the concentration whichis used also in anther culture medium. The 6N1 salts major componentshave been modified to remove ammonium nitrogen. Osmotic potential in theculture medium is maintained with about 12% sucrose and about 400 mg/lproline. Silver nitrate (0.5 mg/l) was included in the medium to modifyethylene activity. The preculture media is further characterized byhaving a pH of about 5.7 to 6.0. Silver nitrate and vitamins do notappear to be crucial to this medium but do improve the efficiency of theresponse.

Whole anther cultures can also be used in the production ofmonocotyledonous plants from a plant culture system. There are somebasic similarities of anther culture methods and microspore culturemethods with regard to the media used. A difference from isolatedmicrospore cultures is that undisrupted anthers are cultured, so that asupport, e.g., a nylon mesh support, is not needed. The first step indeveloping the anther cultures is to incubate tassels at a coldtemperature. A cold temperature is defined as less than about 25° C.More specifically, the incubation of the tassels is preferably performedat about 10° C. A range of 8 to 14° C. is also within the scope of theinvention. The anthers are then dissected from the tassels, preferablyafter surface sterilization using forceps, and placed on solidifiedmedium. An example of such a medium is designated 6N1 -TGR-P4.

The anthers are then treated with environmental conditions that arecombinations of stresses that are capable of diverting microspores fromgametogenesis to embryogenesis. It is believed that the stress effect ofsugar alcohols in the preculture medium, for example, mannitol, isproduced by inducing starvation at the predefined temperature. In oneembodiment, the incubation pretreatment is for about 14 days at 10° C.It was found that treating the anthers in addition with a carbonstructure, an illustrative embodiment being a sugar alcohol, preferablymannitol, produces dramatically higher anther culture response rates asmeasured by the number of eventually regenerated plants, than bytreatment with either cold treatment or mannitol alone. These resultsare particularly surprising in light of teachings that cold is betterthan mannitol for these purposes, and that warmer temperatures interactwith mannitol better.

To incubate the anthers, they are floated on a preculture medium whichdiverts the microspores from gametogenesis, preferably on a mannitolcarbon structure, more specifically, 0.3 M of mannitol plus 50 mg/l ofascorbic acid. Three milliliters is about the total amount in a dish,for example, a tissue culture dish, more specifically, a 60 mm petridish. Anthers are isolated from about 120 spikelets for one dish yieldsabout 360 anthers.

Chromosome doubling agents can be used in the preculture media foranther cultures. Several techniques for doubling chromosome number(Jensen, 1974; Wan et al., 1989) have been described. Colchicine is oneof the doubling agents. However, developmental abnormalities arisingfrom in vitro cloning are further enhanced by colchicine treatments, andprevious reports indicated that colchicine is toxic to microspores. Theaddition of colchicine in increasing concentrations during mannitolpretreatment prior to anther culture and microspore culture has achievedimproved percentages.

An illustrative embodiment of the combination of a chromosome doublingagent and preculture medium is one which contains colchicine. In aspecific embodiment, the colchicine level is preferably about 0.05%. Theanthers remain in the mannitol preculture medium with the additives forabout 10 days at 10° C. Anthers are then placed on maturation media, forexample, that designated 6N1-TGR-P4, for 3 to 6 weeks to induceembryoids. If the plants are to be regenerated from the embryoids, shootregeneration medium is employed, as in the isolated microspore proceduredescribed in the previous sections. Other regeneration media can be usedsequentially to complete regeneration of whole plants.

The anthers are then exposed to embryoid/callus promoting medium, forexample, that designated 6N1-TGR-P4, to obtain callus or embryoids. Theembryoids are recognized visually by identification of embryonic-likestructures. At this stage, the embryoids are transferred progressivelythrough a series of regeneration media. In an illustrative embodiment,the shoot initiation medium comprises BAP (6-benzyl-amino-purine) andNAA (naphthalene acetic acid). Regeneration protocols for isolatedmicrospore cultures and anther cultures are similar.

VIII. Additional Tissue Cultures and Regeneration

The present invention contemplates a corn plant regenerated from atissue culture of the inbred maize plant I363128, or of a hybrid maizeplant produced by crossing I363128. As is well known in the art, tissueculture of corn can be used for the in vitro regeneration of a cornplant. By way of example, a process of tissue culturing and regenerationof corn is described in European Patent Application 0 160 390, thedisclosure of which is incorporated herein by reference. Corn tissueculture procedures are also described in Green and Rhodes (1982) andDuncan et al. (1985). The study by Duncan et al. (1985) indicates that97 percent of cultured plants produced calli capable of regeneratingplants. Subsequent studies have shown that both inbreds and hybridsproduced 91% regenerable calli that produced plants.

Other studies indicate that non-traditional tissues are capable ofproducing somatic embryogenesis and plant regeneration (Songstad et al.,1988; Rao et al., 1986; Conger et al., 1987; the disclosures of whichare incorporated herein by reference). Regenerable cultures, includingType I and Type II cultures, may be initiated from immature embryosusing methods described in, for example, PCT Application WO 95/06128,the disclosure of which is incorporated herein by reference in itsentirety.

Briefly, by way of example, to regenerate a plant of this invention,cells are selected following growth in culture. Where employed, culturedcells are preferably grown either on solid supports or in the form ofliquid suspensions as set forth above. In either instance, nutrients areprovided to the cells in the form of media, and environmental conditionsare controlled. There are many types of tissue culture media comprisingamino acids, salts, sugars, hormones, and vitamins. Most of the mediaemployed to regenerate inbred and hybrid plants have some similarcomponents; the media differ in the composition and proportions of theiringredients depending on the particular application envisioned. Forexample, various cell types usually grow in more than one type of media,but exhibit different growth rates and different morphologies, dependingon the growth media. In some media, cells survive but do not divide.Various types of media suitable for culture of plant cells have beenpreviously described and discussed above.

An exemplary embodiment for culturing recipient corn cells in suspensioncultures includes using embryogenic cells in Type II (Armstrong andGreen, 1985; Gordon-Kamm et al., 1990) callus, selecting for small (I10to 30 mm) isodiametric, cytoplasmically dense cells, growing the cellsin suspension cultures with hormone containing media, subculturing intoa progression of media to facilitate development of shoots and roots,and finally, hardening the plant and readying it metabolically forgrowth in soil.

Meristematic cells (i.e., plant cells capable of continual cell divisionand characterized by an undifferentiated cytological appearance,normally found at growing points or tissues in plants such as root tips,stem apices, lateral buds, etc.) can be cultured (U.S. Pat. No.5,736,369, the disclosure of which is specifically incorporated hereinby reference).

Embryogenic calli are produced essentially as described in PCTApplication WO 95/06128. Specifically, inbred plants or plants fromhybrids produced from crossing an inbred of the present invention withanother inbred are grown to flowering in a greenhouse. Explants from atleast one of the following F₁ tissues: the immature tassel tissue,intercalary meristems and leaf bases, apical meristems, immature earsand immature embryos are placed in an initiation medium which contain MSsalts, supplemented with thiamine, agar, and sucrose. Cultures areincubated in the dark at about 23° C. All culture manipulations andselections are performed with the aid of a dissecting microscope.

After about 5 to 7 days, cellular outgrowths are observed from thesurface of the explants. After about 7 to 21 days, the outgrowths aresubcultured by placing them into fresh medium of the same composition.Some of the intact immature embryo explants are placed on fresh medium.Several subcultures later (after about 2 to 3 months) enough material ispresent from explants for subdivision of these embryogenic calli intotwo or more pieces.

Callus pieces from different explants are not mixed. After furthergrowth and subculture (about 6 months after embryogenic callusinitiation), there are usually between 1 and 100 pieces derivedultimately from each selected explant. During this time of cultureexpansion, a characteristic embryogenic culture morphology develops as aresult of careful selection at each subculture. Any organized structuresresembling roots or root primordia are discarded. Material known fromexperience to lack the capacity for sustained growth is also discarded(translucent, watery, embryogenic structures). Structures with a firmconsistency resembling at least in part the scutelum of the in vivoembryo are selected.

The callus is maintained on agar-solidified MS or N6-type media. Apreferred hormone is 2,4-D. A second preferred hormone is dicamba.Visual selection of embryo-like structures is done to obtainsubcultures. Transfer of material other than that displaying embryogenicmorphology results in loss of the ability to recover whole plants fromthe callus.

Cell suspensions are prepared from the calli by selecting cellpopulations that appear homogeneous macroscopically. A portion of thefriable, rapidly growing embryogenic calli is inoculated into MS or N6Medium containing 2,4-D or dicamba. The calli in medium are incubated atabout 27° C. on a gyrotary shaker in the dark or in the presence of lowlight. The resultant suspension culture is transferred about once everythree to seven days, preferably every three to four days, by takingabout 5 to 10 ml of the culture and introducing this inoculum into freshmedium of the composition listed above (PCT Application WO 95/06128).

For regeneration of type I or type II callus, callus is transferred to asolidified culture medium which includes a lower concentration of 2,4-Dor other auxins than is present in culture medium used for callusmaintenance (PCT Application WO 95/06128, specifically incorporatedherein by reference). Other hormones which can be used in regenerationmedia include dicamba, NAA, ABA, BAP, and 2-NCA. Regeneration of plantsis completed by the transfer of mature and germinating embryos to ahormone-free medium, followed by the transfer of developed plantlets tosoil and growth to maturity. Plant regeneration is described in PCTApplication WO 95/06128.

Cells from the meristem or cells fated to contribute to the meristem ofa cereal plant embryo at the early proernbryo, mid proembryo, lateproembryo, transitional or early coleoptilar stage may be cultured so asto produce a proliferation of shoots or multiple meristems from whichfertile plants may be regenerated. Alternatively, cells from themeristem or cells fated to contribute to the meristem of a cereal plantimmature ear or tassel may be cultured so as to produce a proliferationof shoots or multiple meristems from which fertile plants may beregenerated (U.S. Pat. No. 5,736,369).

Progeny of any generation are produced by taking pollen and selfing,backcrossing, or sibling crossing regenerated plants by methods wellknown to those skilled in the arts. Seeds are collected from theregenerated plants. Alternatively, progeny of any generation may beproduced by pollinating a regenerated plant with its own pollen orpollen of a second maize plant. Using the methods described herein,tissue cultures and immature or mature plant tissues may be used asrecipient cell cultures for the process of genetic transformation.

IX. Processes of Preparing Corn Plants and the Corn Plants Produced bysuch Crosses

The present invention also provides a process of preparing a novel cornplant and a corn plant produced by such a process. In accordance withsuch a process, a first parent corn plant is crossed with a secondparent corn plant wherein at least one of the first and second cornplants is the inbred corn plant I363128. An important aspect of thisprocess is that it can be used for the development of novel inbredlines. For example, the inbred corn plant I363128 could be crossed toany second plant, and the resulting hybrid progeny each selfed for about5 to 7 or more generations, thereby providing a large number ofdistinct, purebreeding inbred lines. These inbred lines could then becrossed with other inbred or non-inbred lines and the resulting hybridprogeny analyzed for beneficial characteristics. In this way, novelinbred lines conferring desirable characteristics could be identified.

In selecting a second plant to cross with I363128 for the purpose ofdeveloping novel inbred lines, it will typically be desired choose thoseplants which either themselves exhibit one or more selected desirablecharacteristics or which exhibit the desired characteristic(s) when inhybrid combination. Examples of potentially desired characteristicsinclude greater yield, better stalks, better roots, resistance toinsecticides, herbicides, pests, and disease, tolerance to heat anddrought, reduced time to crop maturity, better agronomic quality, highernutritional value, and uniformity in germination times, standestablishment, growth rate, maturity, and fruit size. Alternatively, theinbred variety I363128 may be crossed with a second, different inbredplant for the purpose of producing hybrid seed which is sold to farmersfor planting in commercial production fields. In this case, a secondinbred variety is selected which confers desirable characteristics whenin hybrid combination with the first inbred line.

Corn plants (Zea mays L.) can be crossed by either natural or mechanicaltechniques. Natural pollination occurs in corn when wind blows pollenfrom the tassels to the silks that protrude from the tops of therecipient ears. Mechanical pollination can be effected either bycontrolling the types of pollen that can blow onto the silks or bypollinating by hand.

In a preferred embodiment, crossing comprises the steps of:

(a) planting in pollinating proximity seeds of a first and a secondparent corn plant, and preferably, seeds of a first inbred corn plantand a second, distinct inbred corn plant;

(b) cultivating or growing the seeds of the first and second parent cornplants into plants that bear flowers;

(c) emasculating flowers of either the first or second parent cornplant, i.e., treating the flowers so as to prevent pollen production, oralternatively, using as the female parent a male sterile plant, therebyproviding an emasculated parent corn plant;

(d) allowing natural cross-pollination to occur between the first andsecond parent corn plants;

(e) harvesting seeds produced on the emasculated parent corn plant; and,where desired,

(f) growing the harvested seed into a corn plant, preferably, a hybridcorn plant.

Parental plants are typically planted in pollinating proximity to eachother by planting the parental plants in alternating rows, in blocks orin any other convenient planting pattern. Where the parental plantsdiffer in timing of sexual maturity, it may be desired to plant theslower maturing plant first, thereby ensuring the availability of pollenfrom the male parent during the time at which silks on the female parentare receptive to pollen. Plants of both parental parents are cultivatedand allowed to grow until the time of flowering. Advantageously, duringthis growth stage, plants are in general treated with fertilizer and/orother agricultural chemicals as considered appropriate by the grower.

At the time of flowering, in the event that plant I363128 is employed asthe male parent, the tassels of the other parental plant are removedfrom all plants employed as the female parental plant to avoidself-pollination. The detasseling can be achieved manually but also canbe done by machine, if desired. Alternatively, when the female parentcorn plant comprises a cytoplasmic or nuclear gene conferring malesterility, detasseling may not be required. Additionally, a chemicalgametocide may be used to sterilize the male flowers of the femaleplant. In this case, the parent plants used as the male may either notbe treated with the chemical agent or may comprise a genetic factorwhich causes resistance to the emasculating effects of the chemicalagent. Gametocides affect processes or cells involved in thedevelopment, maturation or release of pollen. Plants treated with suchgarnetocides are rendered male sterile, but typically remain femalefertile. The use of chemical gametocides is described, for example, inU.S. Pat. No. 4,936,904, the disclosure of which is specificallyincorporated herein by reference in its entirety. Furthermore, the useof Roundup herbicide in combination with glyphosate tolerant maizeplants to produce male sterile corn plants is disclosed in U.S. patentapplication Ser. No. 08/927,368 and PCT Publication WO 98/44140.

Following emasculation, the plants are then typically allowed tocontinue to grow and natural cross-pollination occurs as a result of theaction of wind, which is normal in the pollination of grasses, includingcorn. As a result of the emasculation of the female parent plant, allthe pollen from the male parent plant is available for pollinationbecause tassels, and thereby pollen bearing flowering parts, have beenpreviously removed from all plants of the inbred plant being used as thefemale in the hybridization. Of course, during this hybridizationprocedure, the parental varieties are grown such that they are isolatedfrom other corn fields to minimize or prevent any accidentalcontamination of pollen from foreign sources. These isolation techniquesare well within the skill of those skilled in this art.

Both parental inbred plants of corn may be allowed to continue to growuntil maturity or the male rows may be destroyed after flowering iscomplete. Only the ears from the female inbred parental plants areharvested to obtain seeds of a novel F₁ hybrid. The novel F₁ hybrid seedproduced can then be planted in a subsequent growing season incommercial fields or, alternatively, advanced in breeding protocols forpurposes of developing novel inbred lines.

Alternatively, in another embodiment of the invention, both first andsecond parent corn plants can come from the same inbred corn plant,i.e., from the inbred designated I363128. Thus, any corn plant producedusing a process of the present invention and inbred corn plant I363128,is contemplated by the current inventor. As used herein, crossing canmean selfing, backcrossing, crossing to another or the same inbred,crossing to populations, and the like. All corn plants produced usingthe inbred corn plant I363128 as a parent are, therefore, within thescope of this invention.

The utility of the inbred plant I363128 also extends to crosses withother species. Commonly, suitable species will be of the familyGraminaceae, and especially of the genera Zea, Tripsacum, Coix,Schlerachne, Polytoca, Chionachne, and Trilobachne, of the tribeMaydeae. Of these, Zea and Tripsacum, are most preferred. Potentiallysuitable for crosses with I363128 can also be the various varieties ofgrain sorghum, Sorghum bicolor (L.) Moench.

A. F₁ Hybrid Corn Plant and Seed Production

Any time the inbred corn plant I363128 is crossed with another,different, corn inbred, a first generation (F₁) corn hybrid plant isproduced. As such, an F₁ hybrid corn plant may be produced by crossingI363128 with any second inbred maize plant. Therefore, any F₁ hybridcorn plant or corn seed which is produced with I363128 as a parent ispart of the present invention.

The goal of the process of producing an F₁ hybrid is to manipulate thegenetic complement of corn to generate new combinations of genes whichinteract to yield new or improved traits (phenotypic characteristics). Aprocess of producing an F₁ hybrid typically begins with the productionof one or more inbred plants. Those plants are produced by repeatedcrossing of ancestrally related corn plants to try to combine certaingenes within the inbred plants.

Corn has a diploid phase which means two conditions of a gene (twoalleles) occupy each locus (position on a chromosome). If the allelesare the same at a locus, there is said to be homozygosity. If they aredifferent, there is said to be heterozygosity. In a completely inbredplant, all loci are homozygous. Because many loci when homozygous aredeleterious to the plant, in particular leading to reduced vigor, lesskernels, weak and/or poor growth, production of inbred plants is anunpredictable and arduous process. Under some conditions, heterozygousadvantage at some loci effectively bars perpetuation of homozygosity.

Inbreeding requires sophisticated manipulation by human breeders. Evenin the extremely unlikely event inbreeding rather than crossbreedingoccurred in natural corn, achievement of complete inbreeding cannot beexpected in nature due to well known deleterious effects of homozygosityand the large number of generations the plant would have to breed inisolation. The reason for the breeder to create inbred plants is to havea known reservoir of genes whose gametic transmission is predictable.

The development of inbred plants generally requires at least about 5 to7 generations of selfing. Inbred plants are then cross-bred in anattempt to develop improved F₁ hybrids. Hybrids are then screened andevaluated in small scale field trials. Typically, about 10 to 15phenotypic traits, selected for their potential commercial value, aremeasured. A selection index of the most commercially important traits isused to help evaluate hybrids. FACT, an acronym for Field AnalysisComparison Trial (strip trials), is an on-farm experimental testingprogram employed by DEKALB Genetics Corporation to perform the finalevaluation of the commercial potential of a product.

During the next several years, a progressive elimination of hybridsoccurs based on more detailed evaluation of their phenotype. Eventually,strip trials (FACT) are conducted to formally compare the experimentalhybrids being developed with other hybrids, some of which werepreviously developed and generally are commercially successful. That is,comparisons of experimental hybrids are made to competitive hybrids todetermine if there was any advantage to further development of theexperimental hybrids. Examples of such comparisons are presentedhereinbelow. After FACT testing is complete, determinations may be madewhether commercial development should proceed for a given hybrid.

When the inbred corn plant I363128 is crossed with another inbred plantto yield a hybrid, the original inbred can serve as either the maternalor paternal plant. For many crosses, the outcome is the same regardlessof the assigned sex of the parental plants.

However, there is often one of the parental plants that is preferred asthe maternal plant because of increased seed yield and productioncharacteristics. Some plants produce tighter ear husks leading to moreloss, for example due to rot. There can be delays in silk formationwhich deleteriously affect timing of the reproductive cycle for a pairof parental inbreds. Seed coat characteristics can be preferable in oneplant. Pollen can be shed better by one plant. Other variables can alsoaffect preferred sexual assignment of a particular cross.

B. F₁ Hybrid Comparisons

As mentioned above, hybrids are progressively eliminated followingdetailed evaluations of their phenotype, including formal comparisonswith other commercially successful hybrids. Strip trials are used tocompare the phenotypes of hybrids grown in as many environments aspossible. They are performed in many environments to assess overallperformance of the new hybrids and to select optimum growing conditions.Because the corn is grown in close proximity, environmental factors thataffect gene expression, such as moisture, temperature, sunlight, andpests, are minimized. For a decision to be made to commercialize ahybrid, it is not necessary that the hybrid be better than all otherhybrids. Rather, significant improvements must be shown in at least sometraits that would create improvements in some niches. An example of sucha comparison is set forth hereinbelow in Table 4.

TABLE 4 Comparative Data of Hybrid 9903904 SI YLD MST STL RTL DRP FLSTDSV ELSTD PHT EHT BAR SG TST ESTR HYBRID NTEST % C BU PTS % % % % M RAT %M INCH INCH % RAT LBS FGDU DAYS 9903904 F 3 103.2 148.0 28.2 15.6 28.1103.4 3.5 96.0 54.0 58.5 1446 116.0 DK665W 84.0 125.4 26.5 12.0 22.7100.6 3.8 86.3 40.0 57.0 1375 115.1 DIFF 19.2 22.6 1.7 3.6 5.4 2.8 −0.39.8 14.0 1.5 71.0 0.8 SIG * 9903904 R 9 109.0 158.0 19.9 7.0 103.1 96.055.5 58.7 114.6 DK665W 92.6 142.2 20.2 4.8 102.5 89.5 45.0 57.7 114.8DIFF 16.4 15.8 −0.3 2.3 0.6 6.5 10.5 1.0 −0.1 SIG + * 9903904 F 54 99.8176.7 23.9 9.1 8.4 2.0 100.8 3.7 100.0 102.4 57.7 3.9 58.8 1420 115.2RX792W 94.0 168.8 22.8 8.4 9.3 0.5 100.0 3.9 101.6 97.5 47.9 5.4 57.91361 114.4 DIFF 5.9 8.0 1.0 0.7 −1.0 1.5 0.8 −0.2 −1.6 5.0 9.7 −1.6 1.059.9 0.8 SIG + * ** + ** ** ** ** ** ** 9903904 R 53 106.4 167.4 20.06.4 1.6 0.0 99.8 3.2 100.2 100.2 54.7 4.4 58.3 1410 115.0 RX792W 90.7152.2 20.2 8.1 8.9 1.0 99.2 5.0 96.9 97.1 50.3 5.2 57.1 1372 114.9 DIFF15.7 15.2 −0.2 −1.6 −7.3 −1.0 0.6 −1.8 3.3 3.1 4.4 −0.8 1.2 38.8 0.1 SIG** ** ** * ** + ** + Significance levels are indicated as: + = 10%, * =5%, ** = 1% LEGEND ABBREVIATIONS: HYBD = Hybrid NTEST = Research/FACT SI% C = Selection Index (percent of check) YLD BU/A = Yield (bushels/acre)MST PTS = Moisture STL % = Stalk Lodging (percent) RTL % = Root Lodging(percent) DRP % = Dropped Ears (percent) FLSTD % M = Final Stand(percent of test mean) SV RAT = Seedling Vigor Rating ELSTD % M = EarlyStand (percent of test mean) PHT INCH = Plant Height (inches) EHT INCH =Ear Height (inches) BAR % = Barren Plants (percent) SG RAT = StaygreenRating TST LBS = Test Weight (pounds) FGDU = GDUs to Shed ESTR DAYS =Estimated Relative Maturity (days)

C. Physical Description of F₁ Hybrids

The present invention provides F₁ hybrid corn plants derived from thecorn plant I363128. Exemplary physical characteristics for a hybridproduced using I363128 as one inbred parent are set forth in Table 5. Anexplanation of terms used in Table 5 can be found in the Definitions,set forth hereinabove.

TABLE 5 Morphological Traits for a Hybrid Made Using I363128 as OneParent CHARACTERISTIC VALUE 1. STALK Diameter (width) cm.  2.3Anthocyanin Basel-Weak Nodes With Brace Roots  1.6 Brace Root ColorFaint Internode Direction Straight Internode Length cm. 14.8 2. LEAFColor Dark Green Length cm. 95.1 Width cm.  9.2 Sheath Anthocyanin WeakSheath Pubescence Moderate Marginal Waves Moderate Longitudinal CreasesMany 3. TASSEL Length cm. 46.3 Spike Length cm. 24.1 Peduncle Length cm.12.8 Branch Number  7.6 Anther Color Salmon Glume Color Red Glume BandAbsent 4. EAR Silk Color Yellow Number Per Stalk  1.0 Position(attitude) Upright Length cm. 18.2 Shape Semi-Conical Diameter cm.  4.7Shank Length cm. 10.8 Husk Bract Short Husk Cover cm.  3.2 Husk OpeningTight Husk Color Fresh Green Husk Color Dry Buff Cob Diameter cm.  2.5Cob Color White Shelling Percent 85.7 5. KERNEL Row Number 15.2 NumberPer Row 38.6 Row Direction Straight Type Dent Cap Color White Side ColorWhite Length (depth) mm. 12.6 Width mm.  8.2 Thickness  3.2 EndospermType Normal Endosperm Color White *These are typical values. Values mavvary due to environment. Other values that are substantially equivalentare also within the scope of the invention. Substantially equivalentrefers to quantitative traits that when compared do not show statisticaldifferences of their means.

X. Genetic Complements

The present invention provides a genetic complement of the inbred cornplant variety designated I363128. Further provided by the invention is ahybrid genetic complement, wherein the complement is formed by thecombination of a haploid genetic complement from I363128 and anotherhaploid genetic complement. Means for determining such a geneticcomplement are well-known in the art.

As used herein, the phrase “genetic complement” means an aggregate ofnucleotide sequences, the expression of which defines the phenotype of acorn plant or a cell or tissue of that plant. By way of example, a cornplant is genotyped to determine a representative sample of the inheritedmarkers it possesses. Markers are alleles at a single locus. They arepreferably inherited in codominant fashion so that the presence of bothalleles at a diploid locus is readily detectable, and they are free ofenvironmental variation, i.e., their heritability is 1. This genotypingis preferably performed on at least one generation of the descendantplant for which the numerical value of the quantitative trait or traitsof interest are also determined. The array of single locus genotypes isexpressed as a profile of marker alleles, two at each locus. The markerallelic composition of each locus can be either homozygous orheterozygous. Homozygosity is a condition where both alleles at a locusare characterized by the same nucleotide sequence or size of a repeatedsequence. Heterozygosity refers to different conditions of the gene at alocus. A preferred type of genetic marker for use with the invention issimple sequence repeats (SSRs), although potentially any other type ofgenetic marker could be used, for example, restriction fragment lengthpolymorphisms (RFLPs), amplified fragment length polymorphisms (AFLPs),single nucleotide polymorphisms (SNPs), and isozymes.

A genetic marker profile of an inbred may be predictive of the agronomictraits of a hybrid produced using that inbred. For example, if an inbredof known genetic marker profile and phenotype is crossed with a secondinbred of known genetic marker profile and phenotype it is possible topredict the phenotype of the F₁ hybrid based on the combined geneticmarker profiles of the parent inbreds. Methods for prediction of hybridperformance from genetic marker data is disclosed in U.S. Pat. No.5,492,547, the disclosure of which is specifically incorporated hereinby reference in its entirety. Such predictions may be made using anysuitable genetic marker, for example, SSRS, RFLPs, AFLPs, SNPs, orisozymes.

SSRs are genetic markers based on polymorphisms in repeated nucleotidesequences, such as microsateilites. A marker system based on SSRs can behighly informative in linkage analysis relative to other marker systemsin that multiple alleles may be present. Another advantage of this typeof marker is that, through use of flanking primers, detection of SSRscan be achieved, for example, by the polymerase chain reaction (PCR™),thereby eliminating the need for labor-intensive Southern hybridization.The PCR™ detection is done by use of two oligonucleotide primersflanking the polymorphic segment of repetitive DNA Repeated cycles ofheat denaturation of the DNA followed by annealing of the primers totheir complementary sequences at low temperatures, and extension of theannealed primers with DNA polymerase, comprise the major part of themethodology. Following amplification, markers can be scored by gelelectrophoresis of the amplification products. Scoring of markergenotype is based on the size (number of base pairs) of the amplifiedsegment.

Means for performing genetic analyses using SSR polymorphisms are wellknown in the art. The SSR analyses reported herein were conducted byCelera AgGen in Davis, Calif. This service is available to the public ona contractual basis. This analysis was carried out by amplification ofsimple repeats followed by detection of marker genotypes using gelelectrophoresis. Markers were scored based on the size of the amplifiedfragment.

The SSR genetic marker profile of the parental inbreds and exemplaryresultant hybrid described herein were determined. Because an inbred isessentially homozygous at all relevant loci, an inbred should, in almostall cases, have only one allele at each locus. In contrast, a diploidgenetic marker profile of a hybrid should be the sum of those parents,e.g., if one inbred parent had the allele 168 (base pairs) at aparticular locus, and the other inbred parent had 172, the hybrid is168.172 by inference. Subsequent generations of progeny produced byselection and breeding are expected to be of genotype 168, 172, or168.172 for that locus position. When the F₁ plant is used to produce aninbred, the locus should be either 168 or 172 for that positionSurprisingly, it has been observed that in certain instances, novel SSRgenotypes arise during the breeding process. For example, a genotype of170 may be observed at a particular locus position from the cross ofparental inbreds with 168 and 172 at that locus. Such a novel SSRgenotype may further define an inbred from the parental inbreds fromwhich it was derived. An SSR genetic marker profile of I363128 ispresented in Table 6.

TABLE 6 SSR Profile of Corn Variety I363128 and Comparative CornVarieties LOCUS I363128 I244339 I465846 BNGL105  92  92  82 BNGL118 127— 127 BNGL244 144 158 196 BNGL426 107 115 107 BNGL589 156 156 156BNGL615 210 210 221 BNGL619 257 245 — DUP14  79 — 103 MC1014 150 161 163MC1018 130 130 162 MC1028 161 148 159 MC1043 147 147 147 MC1046 194 194204 MC1065 230 230 219 MC1070 250 250 244 MC1074 176 180 174 MC1079 173175 — MC1094 178 180 170 MC1108 144 144 120 MC1129 204 188 188 MC1131117 117 111 MC1138 190 196 190 MC1176 254 196 228 MC1182  82  82  82MC1189 226 220 226 MC1191 209 211 — MC1194 143 197 201 MC1208 104 111111 MC1237 159 159 159 MC1265 244 220 222 MC1305 160 160 160 MC1325 181179 — MC1360 149 — 157 MC1456 177 195 — MC1484 124 124 124 MC1520 298 —275 MC1526 114 114 124 MC1538 223 213 223 MC1605 110 102 102 MC1662 161— 136 MC1720 241 241 241 MC1732 102 100 102 MC1740 129 — 129 MC1782 228228 228 MC1784 248 254 248 MC1808 143 143 131 MC1831 182 — 182 MC1834208 208 208 MC1866 119 123 119 MC1890 142 — 188 MC1904 172 183 172MC1917 115 — 161 MC1931 170 176 176 MC2047 144 154 144 MC2086 247 242240 MC2122 240 240 — MC2132 223 223 223 MC2238 219 — 213 MC2259 177 180177 MC2305 190 190 190 NC004 156 156 156 NC009 149 119 — PHI031 194 231— PHI033 257 257 257 PHI037 137 161 — PHI050  90  86  90 PHI061  97  97 97 PHI064  84 104  86 PHI065 148 148 148 PHI072 158 151 158 PHI078 129129 134 PHI101  99  99  99 PHI116 181 181 177 PHI119 168 176 168 PHI120 75 —  75 Primers used to detect SSRs are from Celera AgGen, Inc., 1756Picasso Ave., Davis, CA 95616

Another aspect of this invention is a plant genetic complementcharacterized by a genetic isozyme typing profile. Isozymes are forms ofproteins that are distinguishable, for example, on starch gelelectrophoresis, usually by charge and/or molecular weight. Thetechniques and nomenclature for isozyme analysis are described in, forexample, Stuber et al. ( 1988), which is incorporated by reference.

A standard set of loci can be used as a reference set. Comparativeanalysis of these loci is used to compare the purity of hybrid seeds, toassess the increased variability in hybrids compared to inbreds, and todetermine the identity of seeds, plants, and plant parts. In thisrespect, an isozyme reference set can be used to develop genotypic“fingerprints.” Table 7 lists the identifying numbers of a number ofselected alleles at isozyme loci types for I363128.

TABLE 7 Isozyme Profile of I363128 and a Comparative Corn Variety forSelected Alleles ISOZYME ALLELE LOCI I363128 I244339 I465846 Acph1 4 4 4Idh1 4 4 4 Idh2 6 6 4 Mdh1 6 6 6 Mdh2 6 6 6 Mdh3 16 16 16 Mdh4 12 12 —Mdh5 12 12 12 Pgml 9 9 9 Pgm2 8 8 4 6Pgd1 3.8 3.8 3.8 6Pgd2 5 5 5

The present invention also provides a hybrid genetic complement formedby the combination of a haploid genetic complement of the corn plantI363128 with a haploid genetic complement of a second corn plant. Meansfor combining a haploid genetic complement from the foregoing inbredwith another haploid genetic complement can comprise any method forproducing a hybrid plant from I363128. It is contemplated that such ahybrid genetic complement can be prepared using in vitro regeneration ofa tissue culture of a hybrid plant of this invention.

A hybrid genetic complement contained in the seed of a hybrid derivedfrom I363128 is a further aspect of this invention. Table 8 showsexemplary SSR markers for one hybrid derived from the inbred of thepresent invention.

TABLE 8 Exemplary SSR Markers for Hybrid 9903904 LOCUS Hybrid 9903904BNGL105 092.094 BNGL118 127.110 BNGL244 144.192 BNGL426 107.119 BNGL589156.175 BNGL615 210.227 BNGL619 257.234 DUP14 079.112 MC1014 150.169MC1018 130.130 MC1028 161.159 MC1043 147.175 MC1046 194.218 MC1065230.230 MC1070 250.250 MC1074 176.186 MC1079 173.177 MC1094 178.184MC1108 144.144 MC1129 204.208 MC1131 117.115 MC1138 190.186 MC1176254.220 MC1182 082.106 MC1189 226.219 MC1191 209.238 MC1194 143.177MC1208 104.111 MC1237 159.159 MC1265 244.246 MC1305 160.196 MC1325181.179 MC1360 149.133 MC1456 177.188 MC1484 124.122 MC1520 298.275MC1526 114.122 MC1538 223.239 MC1605 110.128 MC1662 161.167 MC1720241.241 MC1732 102.110 MC1740 129.120 MC1782 228.228 MC1784 248.250MC1808 143.129 MC1834 208.216 MC1890 142.136 MC1904 172.183 MC1917115.109 MC1931 170.170 MC2047 144.146 MC2086 247.242 MC2122 240.254MC2132 223.223 MC2259 177.173 MC2305 190.218 NC004 156.156 NC009 149.119PHI031 194.231 PHI033 257.257 PHI037 137.141 PHI050 090.092 PHI061097.085 PHI064 084.104 PHI065 148.158 PHI072 158.150 PHI078 129.129PHI101 099.099 PHI116 181.177 PHI119 168.176 PHI120 075.075 Primers usedto detect SSRs are from Celera AgGen, Inc., 1756 Picasso Ave., Davis, CA95616

The exemplary hybrid genetic complements of a hybrid may also beassessed by genetic isozyme typing profiles using a standard set of locias a reference set, using, e.g., the same, or a different, set of locito those described above. Table 9 lists exemplary isozyme markers for ahybrid derived from the inbred of the present invention.

TABLE 9 Isozyme Profile for Hybrid 9903904 Loci Isozyme Allele Acph1 4/2Idh1 4/4 Idh2 6/4 Mdh1 6/6 Mdh2   6/3.5 Mdh3 16/16 Mdh4 12/12 Mdh5 12/12Pgm1 9/9 Pgm2 8/4 6-Pgd1 3.8/3.8 6-Pgd2 5/5

All of the compositions and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the compositions and methods of this invention havebeen described in terms of the foregoing illustrative embodiments, itwill be apparent to those of skill in the art that variations, changes,modifications, and alterations may be applied to the composition,methods, and in the steps or in the sequence of steps of the methodsdescribed herein, without departing from the true concept, spirit, andscope of the invention. More specifically, it will be apparent thatcertain agents that are both chemically and physiologically related maybe substituted for the agents described herein while the same or similarresults would be achieved. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope, and concept of the invention as defined by theappended claims.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

Anderson, W. P., Weed Science Principles, West Publishing Company, 1983.

Armstrong and Green, “Establishment and maintenance of friable,embryogenic maize callus and the involvement of L-proline,” Planta,164:207-214, 1985.

Conger, Novak, Afza, Erdelsky, “Somatic Embryogenesis from Cultured LeafSegments of Zea Mays,” Plant Cell Reports, 6:345-347, 1987.

Duncan et al., “The Production of Callus Capable of Plant Regenerationfrom Immature Embryos of Numerous Zea Mays Genotypes,” Planta,165:322-332, 1985.

Fehr, “Theory and Technique,” In: Principles of Cultivar Development,1:360-376, 1987.

Gaillard et al., “Optimization of Maize Microspore Isolation and CultureCondition for Reliable Plant Regeneration,” Plant Cell Reports,10(2):55, 1991.

Gordon-Kamm et al., “Transformation of Maize Cells and Regeneration ofFertile Transgenic Plants,” The Plant Cell, 2:603-618, 1990.

Green and Rhodes, “Plant Regeneration in Tissue Cultures of Maize:Callus Formation from Stem Protoplasts of Corn (Zea Mays L.),” In: Maizefor Biological Research, 367-372, 1982.

Jensen, “Chromosome Doubling Techniques in Haploids,” Haploids andHigher Plants-Advances and Potentials, Proceedings of the FirstInternational Symposium, 1974.

Nienhuis et al., “Restriction Fragment Length Polymorphism Analysis ofLoci Associated with Insect Resistance in Tomato,” Crop Science,27(4):797-803, 1987.

Omirulleh et al., “Activity of a chimeric promoter with the doubled CaMV35S enhancer element in protoplast-derived cells and transgenic plantsin maize,” Plant Mol. Biol., 21(3):415-428, 1993.

Pace et al., “Anther Culture of Maize and the Visualization ofEmbryogenic Microspores by Fluorescent Microscopy,” Theoretical andApplied Genetics, 73:863-869, 1987.

Poehlman et al., “Breeding Field Crops,” 4th Ed., Iowa State UniversityPress, Ames, Iowa, pp 132-155 and 321-344, 1995.

Rao et al., “Somatic Embryogenesis in Glume Callus Cultures,” MaizeGenetics Cooperation Newsletter, 60, 1986.

Songstad et al., “Effect of 1-Aminocyclopropate-1-Carboxylic Acid,Silver Nitrate, and Norbornadiene on Plant Regeneration from MaizeCallus Cultures,” Plant Cell Reports, 7:262-265, 1988.

Sprague and Dudley (eds.), “Corn and Corn Improvement,” 3rd Ed., CropScience of America, Inc., and Soil Science of America, Inc., MadisonWis. pp 881-883 and pp 901-918, 1988.

Stuber et al., “Techniques and scoring procedures for starch gelelectrophoresis of enzymes of maize C. Zea mays, L.,” Tech. Bull., 286,1988.

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Wang et al., “Large-Scale Identification, Mapping, and Genotyping ofSingle-Nucleotide Polymorphisms in the Human Genome,” Science,280:1077-1082, 1998.

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What is claimed is:
 1. A seed of the corn variety I363128, wherein asample of the seed of the corn variety I363128 was deposited under ATCCAccession No. PTA-4494.
 2. A corn plant produced by growing a seed ofthe corn variety I363128, wherein a sample of the seed of the cornvariety I363128 was deposited under ATCC Accession No. PTA4494.
 3. Aplant part of the corn plant of claim
 2. 4. The plant part of claim 3,further defined as pollen.
 5. The plant part of claim 3, further definedas an ovule.
 6. The plant part of claim 3, further defined as a cell. 7.A seed comprising the cell of claim
 6. 8. A tissue culture comprisingthe cell of claim
 6. 9. A corn plant expressing all the physiologicaland morphological characteristics of the corn variety I363128, wherein asample of the seed of the corn variety I363128 was deposited under ATCCAccession No. PTA-4494.
 10. A tissue culture of regenerable cells of aplant of corn variety I363128, wherein the tissue regenerates plantsexpressing all the physiological and morphological characteristics ofthe corn variety I363128, wherein a sample of the seed of the cornvariety I363128 was deposited under ATCC Accession No. PTA-4494.
 11. Thetissue culture of claim 10, wherein the regenerable cells comprise cellsderived from embryos, immature embryos, meristematic cells, immaturetassels, microspores, pollen, leaves, anthers, roots, root tips, silk,flowers, kernels, ears, cobs, husks, or stalks.
 12. The tissue cultureof claim 11, wherein the regenerable cells comprise protoplasts orcallus cells.
 13. A corn plant regenerated from the tissue culture ofclaim 10, wherein the corn plant expresses all of the physiological andmorphological characteristics of the corn variety designated I363128,wherein a sample of the seed of the corn variety I363128 was depositedunder ATCC Accession No. PTA-4494.
 14. A process of producing corn seed,comprising crossing a first parent corn plant with a second parent cornplant, wherein one or both of the first or the second parent corn plantis a plant of the corn variety I363128, wherein a sample of the seed ofthe corn variety I363128 was deposited under ATCC Accession No.PTA-4494, wherein seed is allowed to form.
 15. The process of claim 14,further defined as a process of producing hybrid corn seed, comprisingcrossing a first inbred corn plant with a second, distinct inbred cornplant, wherein the first or second inbred corn plant is a plant of thecorn variety I363128, wherein a sample of the seed of the corn varietyI363128 was deposited under ATCC Accession No. PTA-4494.
 16. The processof claim 15, wherein crossing comprises the steps of: (a) planting theseeds of first and second inbred corn plants; (b) cultivating the seedsof said first and second inbred corn plants into plants that bearflowers; (c) preventing self pollination of at least one of the first orsecond inbred corn plant; (d) allowing cross-pollination to occurbetween the first and second inbred corn plants; and (e) harvestingseeds on at least one of the first or second inbred corn plants, saidseeds resulting from said cross-pollination.
 17. A method of producing amale sterile maize plant comprising transforming the maize plant ofclaim 2 with a nucleic acid molecule that confers male sterility.
 18. Amale sterile maize plant produced by the method of claim
 17. 19. Amethod of producing an herbicide resistant maize plant comprisingtransforming the maize plant of claim 2 with a transgene that confersherbicide resistance.
 20. An herbicide resistant maize plant produced bythe method of claim
 19. 21. The maize plant of claim 20, wherein thetransgene confers resistance to an herbicide selected from the groupconsisting of glyphosate, sulfonylurea, and phosphinothricin.
 22. Amethod of producing an insect resistant maize plant comprisingtransforming the maize plant of claim 2 with a transgene that confersinsect resistance.
 23. An insect resistant maize plant produced by themethod of claim
 22. 24. The maize plant of claim 23, wherein thetransgene encodes a Bacillus thuringiensis Bt endotoxin.
 25. A method ofproducing a disease resistant maize plant comprising transforming themaize plant of claim 2 with a transgene that confers disease resistance.26. A disease resistant maize plant produced by the method of claim 25.27. A method of introducing a desired trait into maize inbred lineI363128 comprising: (a) crossing I363128 plants grown from I363 128seed, representative seed of which has been deposited under ATCCAccession No. PTA-4494, with plants of another maize line that comprisea desired trait to produce F1 progeny plants, wherein the desired traitis selected from the group consisting of male sterility, herbicideresistance, insect resistance, and disease resistance; (b) selecting F1progeny plants that have the desired trait to produce selected F1progeny plants; (c) crossing the selected progeny plants with theI363128 plants to produce backcross progeny plants; (d) selecting forbackcross progeny plants that have the desired trait and traits of maizeinbred line I363128 listed in Table 3 to produce selected backcrossprogeny plants; and (e) repeating steps (c) and (d) three or more timesin succession to produce selected fourth or higher backcross progenyplants that comprise the desired trait and all of the traits of maizeinbred line I363128 listed in Table 3 as determined at the 5%significance level when grown in the same environmental conditions. 28.A plant produced by the method of claim 27, wherein the plant has thedesired trait and all of the traits of maize inbred line I363128 listedin Table 3 as determined at the 5% significance level when grown in thesame environmental conditions.
 29. The plant of claim 28 wherein thedesired trait is herbicide resistance and the resistance is conferred toan herbicide selected from the group consisting of: sulfonylurea,glyphosate, and phosphinothricin.
 30. The plant of claim 28 wherein thedesired trait is insect resistance and the insect resistance isconferred by a transgene encoding a Bacillus thuringiensis Bt endotoxin.31. The plant of claim 28 wherein the desired trait is male sterilityand the trait is conferred by a nucleic acid that confers malesterility.